WO2014085725A1 - Encres à base de biopolymères et leur utilisation - Google Patents

Encres à base de biopolymères et leur utilisation Download PDF

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Publication number
WO2014085725A1
WO2014085725A1 PCT/US2013/072435 US2013072435W WO2014085725A1 WO 2014085725 A1 WO2014085725 A1 WO 2014085725A1 US 2013072435 W US2013072435 W US 2013072435W WO 2014085725 A1 WO2014085725 A1 WO 2014085725A1
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WIPO (PCT)
Prior art keywords
silk
ink
printing
molecular weight
protein
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PCT/US2013/072435
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English (en)
Inventor
Fiorenzo Omenetto
David Kaplan
Hu TAO
Benedetto MARELLI
Miaomiao YANG
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Tufts University
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Application filed by Tufts University filed Critical Tufts University
Priority to EP13858553.4A priority Critical patent/EP2925822A4/fr
Priority to US14/647,470 priority patent/US10035920B2/en
Publication of WO2014085725A1 publication Critical patent/WO2014085725A1/fr
Priority to US16/029,316 priority patent/US10731046B2/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K33/00—Medicinal preparations containing inorganic active ingredients
    • A61K33/24—Heavy metals; Compounds thereof
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K33/00—Medicinal preparations containing inorganic active ingredients
    • A61K33/24—Heavy metals; Compounds thereof
    • A61K33/242—Gold; Compounds thereof
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K41/00—Medicinal preparations obtained by treating materials with wave energy or particle radiation ; Therapies using these preparations
    • A61K41/0052—Thermotherapy; Hyperthermia; Magnetic induction; Induction heating therapy
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
    • A61K47/30—Macromolecular organic or inorganic compounds, e.g. inorganic polyphosphates
    • A61K47/42—Proteins; Polypeptides; Degradation products thereof; Derivatives thereof, e.g. albumin, gelatin or zein
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/15—Heterocyclic compounds having oxygen in the ring
    • C08K5/151—Heterocyclic compounds having oxygen in the ring having one oxygen atom in the ring
    • C08K5/1535—Five-membered rings
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/04—Printing inks based on proteins
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks
    • C09D11/38—Inkjet printing inks characterised by non-macromolecular additives other than solvents, pigments or dyes

Definitions

  • Inkjet printing is a type of computer-based printing that creates a digital image by propelling droplets of ink onto a substrate, typically paper.
  • the concept of inkjet printing has been around for over a century but was made readily accessible to consumers in the latter half of the 20th century.
  • Inkjet printing can be also employed for direct material deposition, which is an emerging manufacturing technique today.
  • particles or 3D dots comprised of materials, such as thermoplastics, metal alloys, and plasters.
  • the present application provides the use of certain biopolymers for preparing printable liquids, i.e., "biopolymer-based inks” or “bio-inks.”
  • biopolymer-based inks i.e., "biopolymer-based inks” or "bio-inks.”
  • the present invention encompasses the recognition that certain polypeptides have material and chemical features that are suitable to be formulated into such inks.
  • the present invention includes the finding that certain polypeptides of structural proteins in origin are especially suited for fabricating micro- and nano-scale (i.e., sub- micron) printed structures.
  • Such structures include two-dimensional (2D) structures and three- dimensional (3D) structures.
  • biopolymer-based inks allow incorporation of a variety of additives (e.g., agents or dopants) for functionahzation, which can be stabilized within the ink.
  • additives e.g., agents or dopants
  • provided bio-ink compositions may further contain other additives, such as excipients, chelating agents, defoamers, etc., among others.
  • the invention is useful for a wide range of applications, including but not limited to, optoelectonics, photonics, therapeutics, tissue engineering such as intelligent implants, synthetic biology, and a variety of consumer products.
  • the invention provides aqueous (i.e., water-based) biopolymer inks.
  • described biopolymer inks comprise a structural protem.
  • described biopolymer inks comprise a structural protein having a specified range or ranges of molecular weights (e.g., fragments). In some embodiments, the specified range includes between about 3.5 kDa and 120 kDa.
  • described biopolymer inks are substantially free of protein fragments exceeding a specified molecular weight. For example, in some embodiments, described biopolymer inks are substantially free of protein fragments over 200 kDa. "Substantially free" means that it is absent or present at a concentration below detection measured by any art-accepted means, such that it is considered negligible.
  • biopolymer inks have a viscosity of between about
  • described biopolymer inks further comprise one or more suitable viscosity-modifying agents (i.e., viscosity modifiers or viscosity adjusters).
  • Biopolymer ink compositions in accordance with the present invention may also contain one or more added agents, or additives, such as dopants.
  • such added agents are stabilized by the ink composition.
  • such added agents are stabilized by the biopolymer (e.g., structural protein) present in the ink composition.
  • the present invention provides a small volume unit of an aqueous composition comprising a low molecular weight structural protein.
  • a unit is an liquid droplet of between about 0.1-100 pL.
  • such an aqueous unit composition contains the low molecular weight structural protein at a concentration of about 0.1-10.0%.
  • such an aqueous unit composition has a viscosity of between about 1-20 centipoise or 1-20 mPa » s.
  • the invention provides an array of printed units, which may be a semisolid or solid form.
  • a printed array may comprise a substrate, upon which a plurality of dot units is deposited, wherein each dot unit comprises a low molecular weight structural protein. Each dot unit is typically between about 0.1-250 ⁇ in diameter. Such dot units may be deposited upon the substrate in a predetermined spatial pattern, including regular and irregular patterns.
  • Printed structures as described herein may be a 2D or a 3D structure.
  • described printed arrays have a resolution of between about 50-
  • such printed structures which are made of dot units as described, may be deposited on a suitable substrate.
  • the invention provides methods for printing a structure.
  • the described methods involve providing a protein-based ink comprising a low molecular weight structural protein of suitable characteristics and depositing the protein-based ink onto a substrate in a predetermined spatial pattem.
  • each liquid droplet has a volume of between about 0.1-100 pL.
  • the invention also includes methods for manufacturing biopolymer-based ink
  • compositions i.e., "bio-inks”
  • provided manufacturing methods include providing an aqueous solution comprising a low molecular weight structural protein (or fragment thereof), and confirming or adjusting the aqueous solution so as to achieve a suitable
  • parameter(s) such as viscosity, surface tension, density (specific gravity), pH, etc.
  • FIG. 1 shows a summary of silk fibroin stabilization effects on immobilized compounds.
  • FIG. 2 shows materials formed with regenerated silk fibroin.
  • FIG. 3 shows a protocol to obtain printable silk inks from raw cocoon.
  • FIG. 4 shows inkjet printing of biopolymer inks on different substrates.
  • FIG. 5 shows an overview of biopolymer ink design, device design, and biopolymer ink- substrate interaction.
  • FIG. 6 shows an inkjet materials printer.
  • FIG. 7 shows a schematic of components of the inkjet printer of FIG. 6.
  • FIG. 8 shows scanning electron microscope (SEM) images of inkjet-printed silver nanoparticle ink before and after sintering at 100 degrees C for 15 minutes.
  • FIG. 9 shows an inkjet printed RFID tag.
  • FIG. 10 illustrates simulated and measured intensity over frequency of the inkjet-printed RFID tag of FIG. 9.
  • FIG. 11 shows an SEM image of human fibrosarcoma cells after inkjet printing.
  • FIG. 12 shows patterns for a pattern editor.
  • FIG. 13 shows patterns for a pattern editor.
  • FIG. 14 shows a cartridge settings interface with voltage settings.
  • FIG. 15 shows a cartridge tab of the cartridge settings interface of FIG. 14.
  • FIG. 16 shows a cleaning cycles tab of the cartridge settings interface of FIG. 14.
  • FIG. 17 shows a piezo actuated nozzle unit of an inkjet printer when a waveform begins.
  • FIG. 18 shows the piezo actuated nozzle unit of FIG. 17 in a first waveform phase.
  • FIG. 19 shows the piezo actuated nozzle unit of FIG. 17 in a second waveform phase.
  • FIG. 20 shows the piezo actuated nozzle unit of FIG. 17 in a third waveform phase.
  • FIG. 21 shows biopolymer lines printed under different voltage: 1) 15v voltage, 65 um; 2) 20v voltage, 100 um; and 3) 25v voltage, 110 um.
  • FIG. 22 shows a waveform for biopolymer ink printing.
  • FIG. 23 shows a one-nozzle printing with a 20 ⁇ line width.
  • FIG. 24 shows a multi-nozzle printing with a 240 ⁇ line width.
  • FIG. 25 shows biopolymer drops.
  • FIG. 26 shows biopolymer dots printed on a silicon wafer.
  • FIG. 27 shows biopolymer dots printed on acrylic.
  • FIG. 28 shows a one-layer biopolymer pattern on a silicon wafer.
  • FIG. 29 shows one-layer lines.
  • FIG. 30 shows a three-layer biopolymer pattern on a silicon wafer.
  • FIG. 31 shows three-layer lines.
  • FIG. 32 shows a twenty-layer biopolymer pattern on a silicon wafer.
  • FIG. 33 shows a cross biopolymer line pattern.
  • FIG. 34 shows a cross biopolymer line pattern with capillary instability.
  • FIG. 35 shows a cross silk line patter with capillary instability, with an enlarged inset view.
  • FIG. 36 shows one-layer 2D biopolymer patterns.
  • FIG. 37 shows one-layer 2D patterns showing diffraction grating patterns.
  • FIG. 38 shows multi-layer 2D patterns.
  • FIG. 39 shows an enlarged partial view of the multi-layer 2D pattern of Fig. 38.
  • FIG. 40 shows a) a silk pattern before annealing and b) the silk pattern after annealing.
  • FIG. 41 shows printing layers vs. thickness of food color biopolymer patterns.
  • FIG. 42 shows printing layers vs. thickness of high refractive index biopolymer patterns.
  • FIG. 43 shows printing layers vs. thickness of biopolymer patterns.
  • FIG. 44 shows a comparison of printing layers vs. thickness of different silk inks.
  • FIG. 45 shows one-layer biopolymer patterns on acrylic.
  • FIG. 46 shows gold nanoparticle doped silk ink in a tube.
  • FIG. 47 shows a gold nanoparticle doped silk dot pattern on paper.
  • FIG. 48 shows an infrared view of the pattern of FIG. 47 when exposed to green light radiation.
  • FIG. 49 shows printed HRP doped biopolymer changing color to blue when sprayed with a tetramehtylbenzidine (TMB) solution.
  • TMB tetramehtylbenzidine
  • FIG. 50 shows two clean bacterial inhibition zones in a bacterial growth petri dish.
  • FIG. 51 shows a bacterial growth inhibition zone in the shape of an arrow.
  • FIG. 52 shows a single color biopolymer pattern on silk textile.
  • FIG. 53 shows a single color biopolymer pattern on silk textile after dry cleaning.
  • FIG. 54 shows multiple-color silk pattern on silk textile before and after alignment optimization.
  • FIG. 55 shows cashmere (keratin) ink in the form of dots on a silicon substrate.
  • FIG. 56 shows cashmere (keratin) ink in the form of a line on a silicon substrate.
  • FIG. 57 shows cashmere (keratin) ink in the form of lines on a silicon substrate.
  • FIG. 58 shows cashmere (keratin) ink in the form of dots on a glass substrate.
  • FIG. 59 shows cashmere (keratin) ink in the form of lines on a glass substrate.
  • Inkjet printing is an easy, inexpensive and widely accessible technology spread around the world for several decades.
  • the fortune of UP is tied to the pervasiveness of personal computing, as for the last two decades it has represented one of the fundamental accessories for any PC workstation.
  • UP is based on the use of electrical actuators to eject picoliter (pL) volumes of liquid from micrometer-wide nozzles onto a substrate in a defined pattern.
  • UP has gained extensive acceptance in microfabrication for basic patterning and rapid fabrication. While the most popular purpose of UP technology remains printing paper documents, it has also been applied in organic electronics, chemical synthesis, sensor fabrication, combinatorial chemistry and biology.
  • Inkjet printing can be divided into two categories: (1) drop-on-demand (DoD) or impulse inkjet, where droplets are generated when required; and (2) continuous inkjet, in which droplets are deflected from a continuous stream to a substrate when needed.
  • DoD drop-on-demand
  • impulse inkjet impulse inkjet
  • continuous inkjet in which droplets are deflected from a continuous stream to a substrate when needed.
  • Inkjet printing can be further subdivided according to the specific means of generating droplets, such as piezoelectric, thermal and electrostatic.
  • Each of these techniques has specific ranges of operation that limit their applicability.
  • Such variables include: operating temperature range, material throughput, reproducibility of droplets, precision of deposition, range of printable viscosities, range of shear forces within the nozzle, reservoir volume and the number of fluids that may be printed during at the same time.
  • Droplet size involves, typically, volumes ranging from 1.5 pL to 5 nL at a rate of 0-25 kHz for drop-on-demand printers (and up to 1 MHz for continuous printheads).
  • Electrohydrodynamic jet printing can produce features as small as 1 ⁇ wide lines, which is typically an order of magnitude smaller than inkjet printing. Naturally, the droplets produced by this technique are also smaller, being in the femto-liter region. Such small droplet sizes are of interest since this means that less material can be dispensed with more spatial control, which couples with the ongoing miniaturization seen in many applications.
  • An open question to be addressed is whether the EHJP droplet ejection method affects the material contained within the ink. Whereas inkjet printers eject their droplets from within the nozzle, EH J printers eject their droplets from outside the nozzle. The ink in an EH J printer forms a droplet that is attached to the nozzle.
  • This dome of ink is charged by a wire contained within the nozzle using voltages up to 200 V, which is necessary to overcome the surface tension and causes a Taylor cone to form.
  • the droplets are ejected from the tip of the cone.
  • This process likely makes protein susceptible to electrical breakdown and droplet deflection during application of inks to substrates.
  • the EHJP process is still in its infancy and it has not yet been applied to the full range of applications that inkjet printing has.
  • EHJP is based on electrostatic forces; meaning that the substrate must be conductive, which is also a limitation.
  • the cost of the technique is another factor to consider.
  • Bio-printing is defined as the process of inkjet printing biomaterials.
  • the field of bio- printing originated in the mid-1990s, with an expansion after the turn in the new millennium.
  • functional materials for sensing biological matter e.g. for glucose and urea
  • in 1987 the first patent for an inkjet-printed enzyme-based biosensor was filed.
  • the robustness and versatility of inkjet printing enabled researchers to modify the technique to meet their needs.
  • the mild conditions afforded by the UP process make it particularly suited for handling biological materials. Minimal sample contamination and waste together with the accurate control and placement of pre-determined quantities of material are also highly appealing features.
  • ⁇ viscosity
  • p density
  • y surface tension
  • a nozzle diameter
  • any protein solution under consideration for printing may be dilute and aqueous, and thus have a density that is already pre-determined; for a given nozzle, the printability of a given protein solution is strongly affected at least by surface tension and viscosity.
  • Proteins formulated as bio-inks are inkjet-printed in aqueous solutions.
  • the composition of the solution influences its surface tension.
  • the applied force that stretches and eventually causes the ejection of the drop is lower than the cohesive counter-force. Indeed, the droplet resists to the external force, resulting in the lack of ejection. Viscosity
  • Proteins are by nature macromolecules, and consequently the viscosity of their solutions is often dramatically affected by changes in concentration. At higher concentrations, the capillary force is insufficient to break the filament of the droplet during the ejection, and the droplet retracts back into the nozzle.
  • the micro-rheological explanation for this behavior is that the coiled and folded polymer chains are elongated in the direction of flow into a stretched state, which is accompanied by a strong increase of the hydrodynamic drag.
  • globular proteins may be easily printable in concentrations of 10 wt% or more with common dampened nozzles, but type I collagen solutions, for example, in concentrations even as low as 0.3-0.5 wt% (a range commonly used for biomedical applications) are unprintable with the same devices. While a common technique for improving the printability of viscous inks is to raise the printing temperature, there are practical restrictions which further limit the printability of structural proteins.
  • Bioprinting processes involve shear rates in the range of 2xl0 4 to 2xl0 6 s "1 ; while such shear rates pose no foreseeable problems for small, globular proteins, they are sufficiently high to compromise the structural integrity of some of their more fragile, larger, counterparts (e.g. structural proteins).
  • Another hindrance in bioprinting structural proteins is the high compression rates used to generate droplets, which may result in the loss of both structural and biological properties, particularly in the absence of stabilizing additives.
  • bio-inks novel, water-based, biopolymer ink compositions
  • the techniques described herein opens a door to a new approach of additive printing that enables the fabrication of biocompatible sub-micron and micro-scale structures with good precision and reproducibility.
  • Non-limiting, exemplary ink formulations as a vehicle suitable for carrying out various embodiments of the present invention include the following components: water (-60-90%); water-soluble solvent such as humectants for viscosity control (-5-30%); dye or pigments (colorants) (-1-10%); surfactant (-0.1-10%)); buffering agent (-0.1-0.5%)); and, other additives ( ⁇ l%o), each of which is measured by weight.
  • an aqueous bio-ink composition in accordance with the present invention comprises the following three components: (z) a structural protein, (ii) a viscosity-modifying agent (i.e., viscosity modifier or viscosity adjuster), such as an amphiphilic agent, and (Hi) water.
  • a structural protein i.e., a structural protein, i.e., a viscosity modifier or viscosity adjuster), such as an amphiphilic agent, and (Hi) water.
  • a viscosity-modifying agent i.e., viscosity modifier or viscosity adjuster
  • the present disclosure encompasses the recognition that it is possible to control certain parameters of an aqueous biopolymer composition, thereby making it possible to be prepared and used as a liquid ink composition that can be readily printed on a substrate.
  • ink compositions upon disposition or printing, can then form semi-solid or solid forms, which allows the fabrication of even sub-micron structures.
  • a structural protein (such as silk fibroin and keratin) is present in a bio-ink composition at a final concentration of about 0.1-10%o by weight, e.g., about 0.1%o, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 0.6%, about 0.7%, about 0.8%, about 0.9%, about 1%), about 1.5%), about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, or greater.
  • structural proteins suitable for carrying out the present invention include the following: fibroins, actins, collagens, catenins, claudins, coilins, elastins, elaunins, extensins, fibrillins, lamins, laminins, keratins, tublins, viral structural proteins, zein proteins (seed storage protein) and any combinations thereof.
  • bio-inks made from a structural protein of molecular weights ranging between about 3.5 kDa and about 120 kDa are particularly useful. In some embodiments, therefore, provided bio-inks of the invention predominantly contain structural protein fragments ranging between about 3.5 kDa and about 120 kDa, e.g., about 3.5 kDa and about 100 kDa, about 5 kDa and about 100 kDa, about
  • fragments correspond to reduced size, relative to the naturally occurring full- length counterpart, such polypeptide fragments are broadly herein referred to as "low molecular weight" protein.
  • polypeptide fragments corresponding to at least a portion of any one of the structural proteins listed above may be used to make a bio-ink described herein.
  • Such polypeptides suitable for practicing the present invention may be produced from various sources, including a regenerated (e.g., purified) protein from natural sources, recombinant proteins produced in heterologous systems, synthetic or chemically produced peptides, or combination of these.
  • described bio-inks may be prepared from a polypeptide corresponding to any one of the list provided above, with or without one or more sequence variations, as compared to the native or wild type counterpart. For example, in some
  • such variants may show at least 85% overall sequence identity as compared to a wild type sequence, e.g., at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% overall sequence identity.
  • bio-ink compositions of the present invention comprise silk fibroin, keratin, or combination thereof.
  • Silk fibroin has a different nature, being extruded from a living organism and changing its structure from globular to highly crystalline during such process.
  • the scope of this work therefore included mimicking the natural silk fibroin extrusion process by inkjet printing regenerated silk solution, pioneering a new way to process this ancient material and providing unprecedented functions to fibroin-based biomaterials.
  • Silk fibroin-based solutions may be formulated as "silk inks" for use in printing.
  • the invention includes silk fibroin-based ink compositions and methods for manufacturing the same.
  • such silk fibroin polypeptide may be a low molecular weight silk fibroin polypeptide, ranging between about 3.5 kDa and about 120 kDa. Low molecular weight silk fibroin is described in detail in U.S. provisional application
  • silk inks are suitable for use in conjunction with commercially available inkjet printers.
  • inkjet printing can be employed for the fabrication of a wide range of nanostructures, using silk inks as a medium. These include two-dimensional (2D) and three-dimensional (3D)
  • silk fibroin useful for the present invention may be that produced by a number of species, including, without limitation: Antheraea mylitta; Antheraea pernyi; Antheraea yamamai; Galleria mellonella; Bombyx mori; Bombyx mandarina; Galleria mellonella; Nephila clavipes; Nephila senegalensis; Gasteracantha mammosa; Argiope aurantia; Araneus diadematus; Latrodectus geometricus; Aranens bicentenarius; Tetragnatha versicolor; Araneus ventricosus; Dolomedes tenebrosus; Euagrus chiso
  • silk for use in accordance with the present invention may be produced by any such organism, or may be prepared through an artificial process, for example, involving genetic engineering of cells or organisms to produce a recombinant silk fibroin polypeptide and/or chemical synthesis.
  • silk is produced by the silkworm, Bombyx mori.
  • silks are modular in design, with large internal repeats flanked by shorter (-100 amino acid) terminal domains (N and C termini).
  • Naturally occurring silk fibroin polypeptides have high molecular weight (200 to 350 kDa or higher) with transcripts of 10,000 base pairs and higher and > 3000 amino acids (reviewed in Omenatto and Kaplan (2010) Science 329: 528-531).
  • the larger modular domains are interrupted with relatively short spacers with hydrophobic charge groups in the case of silkworm silk.
  • N- and C-termini are involved in the assembly and processing of silks, including pH control of assembly.
  • the N- and C-termini are highly conserved, in spite of their relatively small size compared with the internal modules.
  • An exemplary list of silk-producing species and corresponding silk proteins may be found in International Patent Publication Number WO 2011/130335, the entire contents of which are incorporated herein by reference.
  • Cocoon silk produced by the silkworm, Bombyx mori is of particular interest because it offers low-cost, bulk-scale production suitable for a number of commercial applications, such as textile.
  • Silkworm cocoon silk contains two structural proteins, the fibroin heavy chain ( ⁇ 350k Da) and the fibroin light chain ( ⁇ 25k Da), which are associated with a family of nonstructural proteins termed sericin, which glue the fibroin brings together in forming the cocoon.
  • the heavy and light chains of fibroin are linked by a disulfide bond at the C-terminus of the two subunits (Takei,F, Kikuchi,Y., Kikuchi,A., Mizuno,S. and Shimura,K. (1987) J. Cell Biol, 105, 175-180; Tanaka,K, Mori,K. and Mizuno,S. (1993) J. Biochem. (Tokyo), 114, 1-4; Tanaka,K,
  • silk fibroin embraces silk fibroin protein, whether produced by silkworm, spider, or other insect, or otherwise generated (Lucas et al. Adv. Protein Chem, 13: 107-242 (1958)).
  • silk fibroin is obtained from a solution containing a dissolved silkworm silk or spider silk.
  • silkworm silk fibroins are obtained, from the cocoon of Bombyx mori.
  • spider silk fibroins are obtained, for example, from Nephila clavipes.
  • silk fibroins suitable for use in the invention are obtained from a solution containing a genetically engineered silk harvested from bacteria, yeast, mammalian cells, transgenic animals or transgenic plants. See, e.g., WO 97/08315 and U.S. Patent No. 5,245,012, each of which is incorporated herein as reference in its entirety.
  • compositions of the present invention contain fibroin proteins, essentially free of sericins.
  • Provided silk fibroin particles contemplated herein are essentially free of sericins, unless otherwise explicitly specified.
  • Essentially free of sericins means that such compositions contain no (e.g., undetectable) or little (i.e., trace amount) sericin such that one of ordinary skill in the pertinent art will consider negligible for a particular use.
  • silk solutions used to fabricate various compositions of the present invention contain the heavy chain of fibroin, but are essentially free of other proteins. In other embodiments, silk solutions used to fabricate various compositions of the present invention contain both the heavy and light chains of fibroin, but are essentially free of other proteins. In certain embodiments, silk solutions used to fabricate various compositions of the present invention comprise both a heavy and a light chain of silk fibroin; in some such embodiments, the heavy chain and the light chain of silk fibroin are linked via at least one disulfide bond. In some embodiments where the heavy and light chains of fibroin are present, they are linked via one, two, three or more disulfide bonds.
  • fibroin proteins share certain structural features.
  • a general trend in silk fibroin structure is a sequence of amino acids that is characterized by usually alternating glycine and alanine, or alanine alone. Such configuration allows fibroin molecules to self-assemble into a beta-sheet conformation.
  • These "Ala-rich" hydrophobic blocks are typically separated by segments of amino acids with bulky side-groups (e.g., hydrophilic spacers).
  • core repeat sequences of the hydrophobic blocks of fibroin are represented by the following amino acid sequences and/or formulae:
  • GRGGAn SEQ ID NO: 11
  • a fibroin peptide contains multiple hydrophobic blocks, e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 hydrophobic blocks within the peptide. In some embodiments, a fibroin peptide contains between 4-17 hydrophobic blocks. In some embodiments of the invention, a fibroin peptide comprises at least one hydrophilic spacer sequence ("hydrophilic block") that is about 4-50 amino acids in length. Non-limiting examples of the hydrophilic spacer sequences include:
  • TTIIEDLDITIDGADGPI SEQ ID NO: 19
  • TISEELTI SEQ ID NO : 20.
  • a fibroin peptide contains a hydrophilic spacer sequence that is a derivative of any one of the representative spacer sequences listed above. Such derivatives are at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% identical to any one of the hydrophilic spacer sequences. In some embodiments, a fibroin peptide suitable for the present invention contains no spacer.
  • silks are fibrous proteins and are characterized by modular units linked together to form high molecular weight, highly repetitive proteins. These modular units or domains, each with specific amino acid sequences and chemistries, are thought to provide specific functions. For example, sequence motifs such as poly-alanine (poly A) and polyalanine-glycine (poly- AG) are inclined to be beta- sheet- forming; GXX motifs contribute to 31 -helix formation; GXG motifs provide stiffness; and, GPGXX (SEQ ID NO: 22) contributes to beta- spiral formation. These are examples of key components in various silk structures whose positioning and arrangement are intimately tied with the end material properties of silk-based materials (reviewed in Omenetto and Kaplan (2010) Science 329: 528-531).
  • silk fibroin polypeptides of various molecular weights may be used.
  • provided silk fibroin hydrogel comprises silk fibroin polypeptides having an average molecular weight of between about 3.5 kDa and about 350 kDa.
  • suitable ranges of silk fibroin fragments include, but are not limited to: silk fibroin polypeptides have an average molecular weight of between about 3.5 kDa and about 200 kDa; silk fibroin polypeptides have an average molecular weight of between about 3.5 kDa and about 200 kDa; silk fibroin polypeptides have an average molecular weight of between about 3.5 kDa and about 200 kDa; silk fibroin
  • polypeptides have an average molecular weight of between about 3.5 kDa and about 120 kDa; silk fibroin polypeptides have an average molecular weight of between about 25 kDa and about 200 kDa, and so on.
  • Silk fibroin polypeptides that are "reduced" in size, for instance, smaller than the original or wild type counterpart, may be referred to as "low molecular weight silk fibroin.”
  • provided silk fibroin particles are prepared from composition comprising a population of silk fibroin fragments having a range of molecular weights, characterized in that: no more than 15% of total weight of the silk fibroin fragments in the population has a molecular weight exceeding 200 kDa, and at least 50%> of the total weight of the silk fibroin fragments in the population has a molecular weight within a specified range, wherein the specified range is between about 3.5 kDa and about 120 kDa.
  • Keratin is a large family of fibrous structural proteins. Keratin is the key structural material making up the outer layer of human skin. It is also the key structural component of hair and nails. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and insoluble and form strong unmineralized tissues found in reptiles, birds, amphibians, and mammals. The only other biological matter known to approximate the toughness of keratinized tissue is chitin.
  • biopolymer-based ink formulations described herein typically contain at least one viscosity-modifying agent, also referred to as viscosity modifiers or viscosity adjusters.
  • viscosity modifiers also referred to as viscosity modifiers or viscosity adjusters.
  • having the optimal range of viscosity is important for ensuing high quality, reproducible inkjet printing.
  • one or more of any suitable viscosity modifiers maybe used to adjust the viscosity of a bio-ink. It should be noted, however, that certain ink formulations may not require addition of any such viscosity modifiers, so long as the viscosity of the ink composition is already at or near a recommended range.
  • aqueous bio-ink compositions of the present invention contain between about
  • a viscosity modifying agent suitable for use in water-based inks is a water-soluble solvent that regulates or contributes to viscosity control in the liquid ink.
  • the provided bio-ink compositions contain between about 0.5-30%, about 1.0-25%, about 5-20% of viscosity modifying agent agents (measured by volume).
  • the provided bio-ink compositions contain about about 0.5%, about 1.0%, about 2.0%, about 3.0%, about 4.0%, about 5.0%, about 6.0%, about 7.0%, about 8.0%, about 9.0%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 18%, about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31 %, about 32%, about 33%, about 34%, about 35%, of viscosity modifying agent agents (measured by volume).
  • Aqueous bio-ink compositions disclosed described herein may include a viscosity modifier to modulate the final viscosity of the ink formulation.
  • a viscosity modifier to modulate the final viscosity of the ink formulation.
  • any viscosity modifier known and used in the pertinent art can be included in the bio-ink formulations provided herein.
  • humectants may function as viscosity modifiers for the bio-ink composition of the invention.
  • a humectant is a water soluble solvent and any one of a group of hygroscopic substances with hydrating properties, i.e., used to keep things moist. They often are a molecule with several hydrophilic groups, most often hydroxyl groups; however, amines and carboxyl groups, sometimes esterified, can be encountered as well (its affinity to form hydrogen bonds with molecules of water, is the crucial trait).
  • Non- limiting examples of some humectants include: propylene glycol (El 520), hexylene glycol, and butylene glycol; glyceryl triacetate (E1518); vinyl alcohol; neoagarobiose; Sugar alcohols/sugar polyols: glycerol/glycerin, sorbitol (E420), xylitol, maltitol (E965); polymeric polyols (e.g., polydextrose (E1200)); quillaia (E999); urea; aloe vera gel; MP Diol; alpha hydroxy acids (e.g., lactic acid); and, honey.
  • the chemical compound lithium chloride is an excellent (but toxic) humectant, as well.
  • humectants such as glycerol and ethylene glycol are used in water-based inks to prevent the nozzle from clogging.
  • viscosity modifiers examples include, but are not limited to: acrylate esters, acrylic esters, acrylic monomer, aliphatic mono acrylate, aliphatic mono methacrylate, alkoxylated lauryl acrylate, alkoxylated phenol acrylate, alkoxylated tetrahydrofurfuryl acrylate, C 12 -C 14 alkyl methacrylate, aromatic acrylate monomer, aromatic methacrylate monomer, caprolactone acrylate, cyclic trimethylol-propane formal acrylate, cycloaliphatic acrylate monomer, dicyclopentadienyl methacrylate, diethylene glycol methyl ether methacrylate, epoxidized soybean fatty acid esters, epoxidized linseed fatty acid esters, epoxy acrylate, epoxy (meth)acrylate, 2-(2-ethoxy-ethoxy) ethyl acrylate,
  • provided aqueous bio-ink compositions may contain a surfactant agent which works as a wetting and/or penetrating agent.
  • a surfactant agent which works as a wetting and/or penetrating agent.
  • Use of surfactants in water-based inks is, in some embodiments, crucial because even a relatively small amount of a surfactant can significantly modify or affect the surface tension of an aqueous solution (e.g., water or buffers).
  • a surfactant agent is present at concentrations ranging between about 0.05-20%, e.g., between about 0.1-10% (either by volume or by weight) of an ink composition. Relative ratios of ink components
  • silk fibroin solution, an amphiphilic agent (such as a polysorbate) and water are present in a volume ratio of about 17:2:1.
  • silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 17: 1.5:1.5.
  • silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 18:1.5:0.5.
  • silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 16:2:2.
  • silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 16: 1.5:2.5. In some embodiments, silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 16:2.5:1.5. In some embodiments, silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 16:3:1. In some embodiments, silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 15:3:2. In some
  • silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 15:2.5:2.5. In some embodiments, silk fibroin solution, an amphiphilic agent and water are present in a volume ratio of about 15:2:3. Of course, these ratios should be appropriately adjusted when as silk fibroin solution used as the starting component ( ) contains different silk fibroin concentrations, such as 5%, 6%, 7%, 8%, 9% and 10%. In some embodiments, silk fibroin solutions used to prepare silk inks are substantially free of sericin (i.e., degummed).
  • silk fibroin useful for the preparation of silk inks described herein are extracted from cocoons (i.e., natural source of silk fibers). In some embodiments, , silk fibroin useful for the preparation of silk inks described herein are recombinantly produced. In some embodiments, silk fibroin useful for the preparation of silk inks described herein are low molecular weight silk fibroin.
  • Amphiphilic agents useful for preparing silk fibroin-based inks include surfactants.
  • non-ionic detergents are used as an amphiphilic agent for this purpose.
  • silk fibroin-based inks comprise at least one polysorbate.
  • polysorbates include but are not limited to: polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 80, or any combinations thereof.
  • bio-ink compositions of the present invention may further include one or more agent(s) (e.g., dopants and additives) suitable for intended purposes, including therapeutics (e.g., biologically active agents) and biological samples.
  • agent(s) e.g., dopants and additives
  • therapeutics e.g., biologically active agents
  • biological samples e.g., biological samples
  • addition of such agents (or dopants) are said to "functionalize” the ink composition by providing added functionality.
  • suitable dopants one dopant or a combination of compatible dopants
  • Non-limiting examples of suitable agents (or dopants) to be added for functionalization of bio-inks include but are not limited to: conductive or metallic particles; inorganic particles; dyes/pigments; drugs (e.g., antibiotics, small molecules or low molecular weight organic compounds); proteins and fragments or complexes thereof (e.g., enzymes, antigens, antibodies and antigen-binding fragments thereof); cells and fractions thereof (viruses and viral particles; prokaryotic cells such as bacteria;
  • eukaryotic cells such as mammalian cells and plant cells; fungi).
  • the additive is a biologically active agent.
  • biologically active agent refers to any molecule which exerts at least one biological effect in vivo.
  • the biologically active agent can be a therapeutic agent to treat or prevent a disease state or condition in a subject.
  • Biologically active agents include, without limitation, organic molecules, inorganic materials, proteins, peptides, nucleic acids (e.g., genes, gene fragments, gene regulatory sequences, and antisense molecules), nucleoproteins,
  • Classes of biologically active compounds that can be incorporated into the composition described herein include, without limitation, anticancer agents, antibiotics, analgesics, anti-inflammatory agents, immunosuppressants, enzyme inhibitors, antihistamines, anti-convulsants, hormones, muscle relaxants, antispasmodics, ophthalmic agents, prostaglandins, anti-depressants, anti-psychotic substances, trophic factors, osteoinductive proteins, growth factors, and vaccines.
  • the additive is a therapeutic agent.
  • therapeutic agent means a molecule, group of molecules, complex or substance administered to an organism for diagnostic, therapeutic, preventative medical, or veterinary purposes.
  • therapeutic agent includes a "drug” or a "vaccine.” This term include externally and internally administered topical, localized and systemic human and animal pharmaceuticals, treatments, remedies, nutraceuticals, cosmeceuticals, biologicals, devices, diagnostics and contraceptives, including preparations useful in clinical and veterinary screening, prevention, prophylaxis, healing, wellness, detection, imaging, diagnosis, therapy, surgery, monitoring, cosmetics, prosthetics, forensics and the like.
  • This term can also be used in reference to agriceutical, workplace, military, industrial and environmental therapeutics or remedies comprising selected molecules or selected nucleic acid sequences capable of recognizing cellular receptors, membrane receptors, hormone receptors, therapeutic receptors, microbes, viruses or selected targets comprising or capable of contacting plants, animals and/or humans.
  • nucleic acids and compounds comprising nucleic acids that produce a therapeutic effect for example deoxyribonucleic acid (DNA), ribonucleic acid (RNA), nucleic acid analogues (e.g., locked nucleic acid (LNA), peptide nucleic acid (PNA), xeno nucleic acid (XNA)), or mixtures or combinations thereof, including, for example, DNA nanoplexes, siRNA, microRNA, shR A, aptamers, ribozymes, decoy nucleic acids, antisense nucleic acids, RNA activators, and the like.
  • any therapeutic agent can be included in the composition described herein.
  • therapeutic agent also includes an agent that is capable of providing a local or systemic biological, physiological, or therapeutic effect in the biological system to which it is applied.
  • the therapeutic agent can act to control infection or inflammation, enhance cell growth and tissue regeneration, control tumor growth, act as an analgesic, promote anti-cell attachment, and enhance bone growth, among other functions.
  • suitable therapeutic agents can include anti-viral agents, hormones, antibodies, or therapeutic proteins.
  • Other therapeutic agents include prodrugs, which are agents that are not biologically active when administered but, upon administration to a subject are converted to biologically active agents through metabolism or some other mechanism.
  • a silk-based drug delivery composition can contain one therapeutic agent or combinations of two or more therapeutic agents.
  • a therapeutic agent can include a wide variety of different compounds, including chemical compounds and mixtures of chemical compounds, e.g., small organic or inorganic molecules; saccharines; oligosaccharides; polysaccharides; biological macromolecules, e.g., peptides, proteins, and peptide analogs and derivatives; peptidomimetics; antibodies and antigen binding fragments thereof; nucleic acids; nucleic acid analogs and derivatives; an extract made from biological materials such as bacteria, plants, fungi, or animal cells; animal tissues; naturally occurring or synthetic compositions; and any combinations thereof.
  • the therapeutic agent is a small molecule.
  • small molecule can refer to compounds that are "natural product-like,” however, the term “small molecule” is not limited to "natural product-like” compounds. Rather, a small molecule is typically characterized in that it contains several carbon— carbon bonds, and has a molecular weight of less than 5000 Daltons (5 kDa), preferably less than 3 kDa, still more preferably less than 2 kDa, and most preferably less than 1 kDa. In some cases it is preferred that a small molecule have a molecular weight equal to or less than 700 Daltons.
  • Exemplary therapeutic agents include, but are not limited to, those found in Harrison's Principles of Internal Medicine, 13th Edition, Eds. T.R. Harrison et al.
  • Therapeutic agents include the herein disclosed categories and specific examples. It is not intended that the category be limited by the specific examples. Those of ordinary skill in the art will recognize also numerous other compounds that fall within the categories and that are useful according to the present disclosure. Examples include a radiosensitizer, a steroid, a xanthine, a beta-2-agonist bronchodilator, an anti-inflammatory agent, an analgesic agent, a calcium antagonist, an angiotensin-converting enzyme inhibitors, a beta-blocker, a centrally active alpha- agonist, an alpha- 1 -antagonist, an anticholinergic/antispasmodic agent, a vasopressin analogue, an antiarrhythmic agent, an antiparkinsonian agent, an antiangina/antihypertensive agent, an anticoagulant agent, an antiplatelet agent, a sedative, an ansiolytic agent, a peptidic agent, a biopolymeric agent, an antineoplastic agent, a la
  • the pharmaceutically active agent can be coumarin, albumin, steroids such as betamethasone, dexamethasone, methylprednisolone, prednisolone, prednisone, triamcinolone, budesonide, hydrocortisone, and pharmaceutically acceptable hydrocortisone derivatives; xanthines such as theophylline and doxophylline; beta-2-agonist bronchodilators such as salbutamol, fenterol, clenbuterol, bambuterol, salmeterol, fenoterol; antiinflammatory agents, including antiasthmatic anti-inflammatory agents, antiarthritis antiinflammatory agents, and non-steroidal
  • antiinflammatory agents examples of which include but are not limited to sulfides, mesalamine, budesonide, salazopyrin, diclofenac, pharmaceutically acceptable diclofenac salts, nimesulide, naproxene, acetaminophen, ibuprofen, ketoprofen and piroxicam; analgesic agents such as salicylates; calcium channel blockers such as nifedipine, amlodipine, and nicardipine;
  • angiotensin-converting enzyme inhibitors such as captopril, benazepril hydrochloride, fosinopril sodium, trandolapril, ramipril, lisinopril, enalapril, quinapril hydrochloride, and moexipril hydrochloride; beta-blockers (i.e., beta adrenergic blocking agents) such as sotalol
  • hydrochloride timolol maleate, esmolol hydrochloride, carteolol, propanolol hydrochloride, betaxolol hydrochloride, penbutolol sulfate, metoprolol tartrate, metoprolol succinate, acebutolol hydrochloride, atenolol, pindolol, and bisoprolol fumarate; centrally active alpha-2-agonists such as clonidine; alpha- 1 -antagonists such as doxazosin and prazosin; anticholinergic/antispasmodic agents such as dicyclomine hydrochloride, scopolamine hydrobromide, glycopyrrolate, clidinium bromide, flavoxate, and oxybutynin; vasopressin analogues such as vasopressin and
  • antiarrhythmic agents such as quinidine, lidocaine, tocainide hydrochloride, mexiletine hydrochloride, digoxin, verapamil hydrochloride, propafenone hydrochloride, flecainide acetate, procainamide hydrochloride, moricizine hydrochloride, and disopyramide phosphate
  • antiparkinsonian agents such as dopamine, L-Dopa/Carbidopa, selegiline, dihydroergocryptine, pergolide, lisuride, apomorphme, and bromocryptine
  • antiangina agents and antihypertensive agents such as isosorbide mononitrate, isosorbide dinitrate, propranolol, atenolol and verapamil
  • anticoagulant and antiplatelet agents such as Coumadin, warfarin, acetylsalicylic acid, and ticlopidine
  • sedatives such as benzodiazapines and
  • ansiolytic agents such as lorazepam, bromazepam, and diazepam
  • peptidic and biopolymeric agents such as calcitonin, leuprolide and other LH H agonists, hirudin, cyclosporin, insulin, somatostatin, protirelin, interferon, desmopressin, somatotropin, thymopentin, pidotimod, erythropoietin, interleukins, melatonin, granulocyte/macrophage-CSF, and heparin;
  • antineoplastic agents such as etoposide, etoposide phosphate, cyclophosphamide, methotrexate, 5-fiuorouracil, vincristine, doxorubicin, cisp latin, hydroxyurea, leucovorin calcium, tamoxifen, flutamide, asparaginase, altretamine, mitotane, and procarbazine hydrochloride; laxatives such as senna concentrate, casanthranol, bisacodyl, and sodium picosulphate; antidiarrheal agents such as difenoxine hydrochloride, loperamide hydrochloride, furazolidone, diphenoxylate
  • hdyrochloride and microorganisms
  • vaccines such as bacterial and viral vaccines
  • antimicrobial agents such as penicillins, cephalosporins, and macrolides
  • antifungal agents such as imidazolic and triazolic derivatives
  • nucleic acids such as D A sequences encoding for biological proteins, and antisense oligonucleotides.
  • Anti-cancer agents include alkylating agents, platinum agents, antimetabolites, topoisomerase inhibitors, antitumor antibiotics, antimitotic agents, aromatase inhibitors, thymidylate synthase inhibitors, DNA antagonists, farnesyltransferase inhibitors, pump inhibitors, histone acetyltransferase inhibitors, metalloproteinase inhibitors, ribonucleoside reductase inhibitors, TNF alpha agonists/antagonists, endothelinA receptor antagonists, retinoic acid receptor agonists, immuno-modulators, hormonal and antihormonal agents, photodynamic agents, and tyrosine kinase inhibitors.
  • Antibiotics include aminoglycosides (e.g., gentamicin, tobramycin, netilmicin, streptomycin, amikacin, neomycin), bacitracin, corbapenems (e.g., imipenenVcislastatin), cephalosporins, colistin, methenamine, monobactams (e.g., aztreonam), penicillins (e.g., penicillin G, penicillinV, methicillin, natcillin, oxacillin, cloxacillin, dicloxacillin, ampicillin, amoxicillin, carbenicillin, ticarcillin, piperacillin, mezlocillin, azlocillin), polymyxin B, quinolones, and vancomycin; and bacteriostatic agents such as chloramphenicol, clindanyan, macrolides (e.g., erythromycin, azithromycin, clarithromycin),
  • Enzyme inhibitors are substances which inhibit an enzymatic reaction.
  • enzyme inhibitors include edrophonium chloride, N-methylphysostigmine, neostigmine bromide, physostigmine sulfate, tacrine, tacrine, 1 -hydroxy maleate, iodotubercidin, p-bromotetramiisole, 10-(alpha-diethylaminopropionyl)-phenothiazine hydrochloride, calmidazolium chloride, hemicholinium-3,3,5-dinitrocatechol, diacylglycerol kinase inhibitor I, diacylglycerol kinase inhibitor II, 3-phenylpropargylamine, N°-monomethyl-Larginine acetate, carbidopa, 3- hydroxybenzylhydrazine, hydralazine, clorgyline, deprenyl, hydroxylamine, iproni
  • Antihistamines include pyrilamine, chlorpheniramine, and tetrahydrazoline, among others.
  • Anti-inflammatory agents include corticosteroids, nonsteroidal anti-inflammatory drugs (e.g., aspirin, phenylbutazone, indomethacin, sulindac, tolmetin, ibuprofen, piroxicam, and fenamates), acetaminophen, phenacetin, gold salts, chloroquine, D-Penicillamine, methotrexate colchicine, allopurinol, probenecid, and sulfinpyrazone.
  • Muscle relaxants include mephenesin, methocarbomal, cyclobenzaprine hydrochloride, trihexylphenidyl hydrochloride, levodopa/carbidopa, and biperiden.
  • Anti-spasmodics include atropine, scopolamine, oxyphenonium, and papaverine.
  • Analgesics include aspirin, phenybutazone, idomethacin, sulindac, tolmetic, ibuprofen, piroxicam, fenamates, acetaminophen, phenacetin, morphine sulfate, codeine sulfate, meperidine, nalorphine, opioids (e.g., codeine sulfate, fentanyl citrate, hydrocodone bitartrate, loperamide, morphine sulfate, noscapine, norcodeine, normorphine, thebaine, nor- binaltorphimine, buprenorphine, chlomaltrexamine, funaltrexamione, nalbuphine, nalorphine, naloxone, naloxonazine, naltrexone, and naltrindole), procaine, lidocain, tetracaine and dibucaine.
  • Ophthalmic agents include sodium fluorescein, rose bengal, methacholine, adrenaline, cocaine, atropine, alpha-chymotrypsin, hyaluronidase, betaxalol, pilocarpine, timolol, timolol salts, and combinations thereof
  • Prostaglandins are art recognized and are a class of naturally occurring chemically related long-chain hydroxy fatty acids that have a variety of biological effects.
  • Anti-depressants are substances capable of preventing or relieving depression.
  • Examples of anti-depressants include imipramine, amitriptyline, nortriptyline, protriptyline, desipramine, amoxapine, doxepin, maprotiline, tranylcypromine, phenelzine, and isocarboxazide.
  • Trophic factors are factors whose continued presence improves the viability or longevity of a cell
  • trophic factors include, without limitation, platelet-derived growth factor (PDGP), neutrophil-activating protein, monocyte chemoattractant protein, macrophage-inflammatory protein, platelet factor, platelet basic protein, and melanoma growth stimulating activity;
  • PDGP platelet-derived growth factor
  • neutrophil-activating protein neutrophil-activating protein
  • monocyte chemoattractant protein monocyte chemoattractant protein
  • macrophage-inflammatory protein platelet factor
  • platelet factor platelet basic protein
  • melanoma growth stimulating activity melanoma growth stimulating activity
  • epidermal growth factor transforming growth factor (alpha), fibroblast growth factor, platelet- derived endothelial cell growth factor, insulin-like growth factor, glial derived growth neurotrophic factor, ciliary neurotrophic factor, nerve growth factor, bone growth/cartilage- inducing factor (alpha and beta), bone morphogenetic proteins, interleukins (e.g., interleukin inhibitors or interleukin receptors, including interleukin 1 through interleukin 10), interferons (e.g., interferon alpha, beta and gamma), hematopoietic factors, including erythropoietin, granulocyte colony stimulating factor, macrophage colony stimulating factor and granulocyte- macrophage colony stimulating factor; tumor necrosis factors, and transforming growth factors (beta), including beta-1, beta-2, beta-3, inhibin, and activin.
  • interleukins e.g., interleukin inhibitors or interleukin
  • Hormones include estrogens (e.g., estradiol, estrone, estriol, diethylstibestrol, quinestrol, chlorotrianisene, ethinyl estradiol, mestranol), anti-estrogens (e.g., clomiphene, tamoxifen), progestins (e.g., medroxyprogesterone, norethindrone, hydroxyprogesterone, norgestrel), antiprogestin (mifepristone), androgens (e.g, testosterone cypionate, fluoxymesterone, danazol, testo lactone), anti-androgens (e.g., cyproterone acetate, flutamide), thyroid hormones (e.g., triiodothyronne, thyroxine, propylthiouracil, methimazole, and iodixode), and pituitary hormones (e.
  • the additive is an agent that stimulates tissue formation, and/or healing and regrowth of natural tissues, and any combinations thereof.
  • Agents that increase formation of new tissues and/or stimulates healing or regrowth of native tissue at the site of injection can include, but are not limited to, fibroblast growth factor (FGF), transforming growth factor-beta (TGF-beta, platelet-derived growth factor (PDGF), epidermal growth factors (EGFs), connective tissue activated peptides (CTAPs), osteogenic factors including bone morphogenic proteins, heparin, angiotensin II (A-II) and fragments thereof, insulin-like growth factors, tumor necrosis factors, interleukins, colony stimulating factors, erythropoietin, nerve growth factors, interferons, biologically active analogs, fragments, and derivatives of such growth factors, and any combinations thereof.
  • FGF fibroblast growth factor
  • TGF-beta transforming growth factor-beta
  • PDGF platelet-derived growth
  • the silk composition can further comprise at least one additional material for soft tissue augmentation, e.g., dermal filler materials, including, but not limited to, poly(methyl methacrylate) microspheres, hydroxylapatite, poly(L-lactic acid), collagen, elastin, and glycosaminoglycans, hyaluronic acid, commercial dermal filler products such as BOTOX® (from Allergan), DYSPORT®, COSMODERM®, EVOLENCE®, RADIESSE®,
  • dermal filler materials including, but not limited to, poly(methyl methacrylate) microspheres, hydroxylapatite, poly(L-lactic acid), collagen, elastin, and glycosaminoglycans, hyaluronic acid, commercial dermal filler products such as BOTOX® (from Allergan), DYSPORT®, COSMODERM®, EVOLENCE®, RADIESSE®,
  • the additive is a wound healing agent.
  • a wound healing agent is a compound or composition that actively promotes wound healing process.
  • exemplary wound healing agents include, but are not limited to dexpanthenol; growth factors; enzymes, hormones; povidon-iodide; fatty acids; anti-inflammatory agents; antibiotics;
  • nucleosides such as adenosine
  • nucleotides such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP);
  • neutotransmitter/neuromodulators such as acetylcholine and 5-hydroxytryptamine (serotonin/5 - HT); histamine and catecholamines, such as adrenalin and noradrenalin; lipid molecules, such as sphingosine-1 -phosphate and lysophosphatidic acid; amino acids, such as arginine and lysine; peptides such as the bradykinins, substance P and calcium gene-related peptide (CG P); nitric oxide; and any combinations thereof.
  • neutotransmitter/neuromodulators such as acetylcholine and 5-hydroxytryptamine (serotonin/5 - HT); histamine and catecholamines, such as adrenalin and noradrenalin; lipid molecules, such as sphingosine-1 -phosphate and lysophosphatidic acid; amino acids, such as arginine and lysine; peptides such as the bradykin
  • the active agents described herein are immunogens.
  • the immunogen is a vaccine.
  • Most vaccines are sensitive to environmental conditions under which they are stored and/or transported. For example, freezing may increase reactogenicity (e.g., capability of causing an immunological reaction) and/or loss of potency for some vaccines (e.g., HepB, and DTaP/IPV/HIB), or cause hairline cracks in the container, leading to contamination.
  • some vaccines e.g., BCG, Varicella, and MMR
  • Many vaccines e.g., BCG, MMR, Varicella, Meningococcal C Conjugate, and most DTaP-containing vaccines) are light sensitive.
  • compositions and methods described herein also provide for stabilization of vaccines regardless of the cold chain and/or other environmental conditions.
  • the additive is a cell, e.g., a biological cell.
  • Cells useful for incorporation into the composition can come from any source, e.g., mammalian, insect, plant, etc.
  • the cell can be a human, rat or mouse cell.
  • cells to be used with the compositions described herein can be any types of cells.
  • the cells should be viable when encapsulated within compositions.
  • cells that can be used with the composition include, but are not limited to, mammalian cells (e.g. human cells, primate cells, mammalian cells, rodent cells, etc.), avian cells, fish cells, insect cells, plant cells, fungal cells, bacterial cells, and hybrid cells.
  • exemplary cells that can be can be used with the compositions include platelets, activated platelets, stem cells, totipotent cells, pluripotent cells, and/or embryonic stem cells.
  • exemplary cells that can be encapsulated within compositions include, but are not limited to, primary cells and/or cell lines from any tissue. For example, cardiomyocytes, myocytes, hepatocytes, keratinocytes, melanocytes, neurons, astrocytes, embryonic stem cells, adult stem cells, hematopoietic stem cells, hematopoietic cells (e.g.
  • ameloblasts fibroblasts, chondrocytes, osteoblasts, osteoclasts, neurons, sperm cells, egg cells, liver cells, epithelial cells from lung, epithelial cells from gut, epithelial cells from intestine, liver, epithelial cells from skin, etc, and/or hybrids thereof, can be included in the silk/platelet compositions disclosed herein.
  • Those skilled in the art will recognize that the cells listed herein represent an exemplary, not comprehensive, list of cells.
  • Cells can be obtained from donors (allogenic) or from recipients (autologous). Cells can be obtained, as a non-limiting example, by biopsy or other surgical means known to those skilled in the art.
  • the cell can be a genetically modified cell.
  • a cell can be genetically modified to express and secrete a desired compound, e.g. a bioactive agent, a growth factor, differentiation factor, cytokines, and the like.
  • a desired compound e.g. a bioactive agent, a growth factor, differentiation factor, cytokines, and the like.
  • Differentiated cells that have been reprogrammed into stem cells can also be used.
  • bio-ink compositions provided herein can include a colorant, such as a pigment or dye or combination thereof. Any organic and/or inorganic pigments and dyes can be included in the inks.
  • Exemplary pigments suitable for use in the present invention include International Color Index or C.I. Pigment Black Numbers 1 , 7, 1 1 and 31 , C.I. Pigment Blue Numbers 15, 15 : 1 , 15 :2, 15 :3, 15 :4, 15 :6, 16, 27, 29, 61 and 62, C.I. Pigment Green
  • carbon black pigment such as Regal 330, Cabot Corporation
  • quinacridone pigments Quinacridone Magenta (228-0122), available from Sun Chemical Corporation, Fort Lee, N.J.
  • diarylide yellow pigment such as AAOT Yellow (274-1788) available from Sun Chemical Corporation
  • the classes of dyes suitable for use in present invention can be selected from acid dyes, natural dyes, direct dyes (either cationic or anionic), basic dyes, and reactive dyes.
  • the acid dyes also regarded as anionic dyes, are soluble in water and mainly insoluble in organic solvents and are selected, from yellow acid dyes, orange acid dyes, red acid dyes, violet acid dyes, blue acid dyes, green acid dyes, and black acid dyes.
  • European Patent 0745 51 describes a number of acid dyes that are suitable for use in the present invention.
  • Exemplary yellow acid dyes include Acid Yellow 1 International Color Index or C.I. 10316); Acid Yellow 7 (C.I. 56295); Acid Yellow 17 (C.I. 18965); Acid Yellow 23 (C.I. 19140); Acid Yellow 29 (C.I. 18900); Acid Yellow 36 (C.I.
  • Acid Yellow 42 (C.I. 22910); Acid Yellow 73 (C.I. 45350); Acid Yellow 99 (C.I.
  • Exemplary orange acid dyes include Acid Orange 1 (C.I. 13090/1); Acid Orange 10 (C.I. 16230).; Acid Orange 20 (C.I. 14603); Acid Orange 76 (C.I. 18870); Acid Orange 142; Food Orange 2 (C.I. 15980); and Orange B.
  • Exemplary red acid dyes include Acid Red 1. (C.I. 18050); Acid Red 4 (C.I. 14710); Acid Red 18 (C.I. 16255), Acid Red 26 (C.I. 16150); Acid Red 2.7 (C.I. as Acid Red 51 (C.I. 45430, available from BASF Corporation, Mt. Olive, N.J.) Acid Red 52 (C.I. 45100); Acid Red 73 (C.I. 27290); Acid Red 87 (C. I. 45380); Acid Red 94 (C.I. 45440) Acid Red 194;. and Food Red 1 (C.I. 14700).
  • Exemplary violet acid dyes include Acid Violet 7 (C.I. 18055); and Acid Violet 49 (C.I. 42640).
  • Exemplary blue acid dyes include Acid Blue 1 (C.I. 42045); Acid Blue 9 (C.I. 42090); Acid Blue 22 (C.I. 42755); Acid Blue 74 (C.I. 73015); Acid Blue 93 (C.I. 42780); and Acid Blue 158A (C.I. 15050).
  • Exemplary green acid dyes include Acid Green 1 (C.I.
  • Exemplary black acid dyes include Acid Black 1 (C.I. 20470); Acid Black 194 (Basantol® X80, available from BASF Corporation, an azo/1 :2 CR-complex.
  • Exemplary direct dyes for use in the present invention include Direct Blue 86 (C.I.
  • Exemplary natural dyes for use in the present invention include Alkanet (C.I. 75520,75530); Annafto (C.I. 75120); Carotene (C.I. 75130); Chestnut; Cochineal (C.I.75470); Cutch (C.I. 75250, 75260); Divi-Divi; Fustic (C.I. 75240); Hypernic (C.I. 75280); Logwood (C.I. 75200); Osage Orange (C.I. 75660); Paprika; Quercitron (C.I. 75720); Sanrou (C.I. 7 100) ; Sandal Wood (C.I. 75510, 75540, 75550, 75560); Sumac; and Tumeric (C.I. 75300).
  • Exemplary reactive dyes for use in the present invention include Reactive Yellow 37 (monoazo dye);
  • Reactive Black 31 (disazo dye); Reactive Blue 77 (phthalo cyanine dye) and Reactive Red 180 and Reactive Red 108 dyes. Suitable also are the colorants described in The Printing Ink Manual (5th ed., Leach et al. eds. (2007), pages 289-299. Other organic and inorganic pigments and dyes and combinations thereof can be used to achieve the colors desired.
  • bio-ink compositions described herein can contain UV fluorophores that are excited in the UV range and emit light at a higher wavelength (typically 400 nm and above).
  • UV fluorophores include but are not limited to materials from the coumarin, benzoxazole, rhodamine, napthalimide, perylene, benzanthrones, benzoxanthones or benzothia- xanthones families.
  • a UV fluorophore such as an optical brightener for instance
  • the amount of colorant, when present, generally is between 0.05% to 5% or between 0.1% and 1% based on the weight of the bio-ink composition.
  • the amount of pigment/dye generally is present in an amount of from at or about 0.1 wt% to at or about 20 wt% based on the weight of the ink composition.
  • a non-white ink can include 15 wt% or less pigment/dye, or 10 wt% or less pigment/dye or 5 wt% pigment/dye, or 1 wt% pigment/dye based on the weight of the ink composition.
  • a non- white ink can include 1 wt% to 10 wt%, or 5 wt% to 15 wt%, or 10 wt% to 20 wt% pigment/dye based on the weight of the ink composition.
  • a non- white ink can contain an amount of dye/pigment that is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15%), 16 wt%>, 17 wt%>, 18 wt%>, 19 wt%> or 20 wt%> based on the weight of the ink composition.
  • the amount of white pigment generally is present in an amount of from at or about 1 wt% to at or about 60 wt% based on the weight of the ink composition. In some applications, greater than 60 wt% white pigment can be present.
  • Preferred white pigments include titanium dioxide (anatase and rutile), zinc oxide, lithopone (calcined coprecipitate of barium sulfate and zinc sulfide), zinc sulfide, blanc fixe and alumina hydrate and combinations thereof, although any of these can be combined with calcium carbonate.
  • a white ink can include 60 wt% or less white pigment, or 55 wt% or less white pigment, or 50 wt% white pigment, or 45 wt% white pigment, or 40 wt% white pigment, or 35 wt% white pigment, or 30 wt% white pigment, or 25 wt% white pigment, or 20 wt% white pigment, or 15 wt% white pigment, or 10 wt% white pigment, based on the weight of the ink composition.
  • a white ink can include 5 wt% to 60 wt%, or 5 wt% to 55 wt%, or 10 wt% to 50 wt%, or 10 wt% to 25 wt%, or 25 wt% to 50 wt%, or 5 wt% to 15 wt%, or 40 wt% to 60 wt% white pigment based on the weight of the ink composition.
  • a non-white ink can an amount of dye/pigment that is 5%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45%, 46 wt%
  • provided bio-ink compositions depends on the usage and the storage conditions. In some embodiments, storage in a refrigerator at 4 degree C when finishing printing is recommended. In some embodiments, provided bio-inks (with our without dopants) may be stored without refrigeration, such as at room temperature (typically between about 18-26°C) for an extended duration of time without significant loss of function.
  • provided bio-inks may be stored at room temperature (typically between about 18-26°C) for an extended duration of time, such as at least for 1 week, at least for 2 weeks, at least for 3 weeks, at least for 4 weeks, at least for 6 weeks, at least for 2 months, at least for 3 months, at least for 4 months, at least for 5 months, at least for 6 months, at least for 9 months, at least for 12 months, at least for 15 months, at least for 18 months, and at least for 24 months, or longer, without significant loss of function.
  • room temperature typically between about 18-26°C
  • an extended duration of time such as at least for 1 week, at least for 2 weeks, at least for 3 weeks, at least for 4 weeks, at least for 6 weeks, at least for 2 months, at least for 3 months, at least for 4 months, at least for 5 months, at least for 6 months, at least for 9 months, at least for 12 months, at least for 15 months, at least for 18 months, and at least for 24 months, or longer, without significant loss of function.
  • provided bio-inks may be stored at elevated temperature (between about 27-40°C) for at least part of the duration of storage, for an extended duration of time, such as at least for 1 week, at least for 2 weeks, at least for 3 weeks, at least for 4 weeks, at least for 6 weeks, at least for 2 months, at least for 3 months, at least for 4 months, at least for 5 months, at least for 6 months, at least for 9 months, at least for 12 months, at least for 15 months, at least for 18 months, and at least for 24 months, or longer, without significant loss of function.
  • bio-ink compositions have suitable properties as measured by surface tension, viscosity and/or pH.
  • a bio-ink composition of the present disclosure is prepared as described herein, so that the ink composition has, for example, surface tension ranges between about 24-50 dynes/cm at room temperature, between about 28-44 dynes/cm at room temperature, between about 30-38 dynes/cm at room temperature; viscosity of between about 8-10 centipoise at room temperature.
  • such ink composition has a pH value of between about 5-9, such as between 6-7, between 5.5-7.5.
  • room temperature is typically between about 18-26 °C, and also referred to as “ambient” condition.
  • the phrase “room temperature” and “ambient temperature (or condition)” may include temperatures such as about 18 °C, about 19 °C, about 20 °C, about 21 °C, about 22 °C, about 23 °C, about 24 °C, about 25 °C, about 26 °C, and so on, unless otherwise specified.
  • Another aspect of the invention provides methods for preparing bio-inks, such as silk fibroin inks.
  • An exemplary protocol for preparing a silk fibroin ink in accordance with the present disclosure is provided below. Preparation of low molecular weight structural proteins
  • the present invention encompasses the recognition that certain structural proteins can be processed further to be made suitable for bio-printing described herein, thereby overcoming previously existed hurdles that had prevented the use of certain structural proteins for printing purposes.
  • such methods involve extraction of structural proteins (such as silk fibroin) under high temperature, such as between about 101-135°C, between about 105-130°C, between about 110-130°C, between about 115-125°C, between about 118-123°C, e.g., about 115°C, 116°C, 117°C, 118°C, 119°C, 120°C, 121°C, 122°C, 123°C, 124°C, 125°C.
  • structural proteins such as silk fibroin
  • provided methods in some embodiments involve extraction of structural proteins (such as silk fibroin) under elevated pressure, such as about 5 psi, 6 psi, 7 psi, 8 psi, 9 psi, 10 psi, 11 psi, 12 psi, 13 psi, 14 psi, 15 psi, 16 psi, 17 psi, 18 psi, 19 psi, 20 psi, 21 psi, 22 psi, 23 psi, 24 psi, 25 psi, 30 psi, 31 psi, 32 psi, 33 psi, 34 psi and 35 psi.
  • structural proteins such as silk fibroin
  • structural proteins are extracted under high temperature and under elevated pressure, e.g., at about 110-130°C and about 10-20 psi for a duration suitable to produce a protein solution that would easily go through a 0.2 ⁇ filter.
  • structural proteins are extracted under high temperature and under elevated pressure, e.g., at about 110-130°C and about 10-20 psi for about 60-180 minutes.
  • structural proteins are extracted under high temperature and under elevated pressure, e.g., at about 116-126°C and about 12-20 psi for about 90-150 minutes.
  • the following example process may be performed to obtain ⁇ 40 mL of silk solution with a concentration of ⁇ 6.25 % (wt/vol); if more volumes are needed, the materials can be scaled appropriately.
  • Viscosity 8 - 10 centipoise at room temperature
  • the ratio of the mixture is optimized for Tween 20 and other biological or chemical surfactant (for example, glycol, ether, and etc.) can be also used with modifications of the mixture ratio.
  • Surface treatment of the printing nozzle(s) can also improve the formation of silk ink drops.
  • SF silk fibroin
  • SF is a structural protein, like collagen, but with a unique feature: it is produced from the extrusion of an amino-acidic solution by a living complex organism (while collagen is produced in the extracellular space by self-assembly of cell-produced monomers).
  • SF properties are derived from its structure, which consists of hydrophobic blocks staggered by hydrophilic, acidic spacers. In its natural state, SF is organized in ⁇ -sheet crystals alternated with amorphous regions, which provide strength and resilience to the protein.
  • SF is indeed considered a platform technology in biomaterials fabrication as its robustness and qualities bring the assets to add a large portfolio of distinct features (e.g. nanopatterning, biochemical functionalization) to the final construct.
  • Processing of regenerated SF generally involves the partial or total dehydration of a fibroin solution (protein content of 1-15 wt%) to form films, sponges, gels, spheres (micron- to nano-sized) and foams with numerous techniques (e.g. solvent casting, freeze drying, salt leaching, sonication).
  • a fibroin solution protein content of 1-15 wt%
  • foams with numerous techniques (e.g. solvent casting, freeze drying, salt leaching, sonication).
  • solvent casting freeze drying, salt leaching, sonication
  • the present invention provides means for achieving a very small unit volume of a bio-ink composition formed as liquid droplets for carrying out printing.
  • the present application provides an aqueous unit composition (i.e., a liquid droplet) having a volume of between about 0.1-100 pL.
  • each droplet has a volume of between about 0.5-50 pL, between about 0.5-25 pL, between about 0.5-20 pL, between about 0.5-15 pL, between about 0.5-10 pL, between about 1.0-40 pL, between about 1.0-30 pL, between about 1.0-25 pL, between about 1.0-20 pL, between about 1.0-15 pL, between about 1.0-10 pL.
  • a unit volume of a single droplet of a bio-ink described herein is about 0.5 pL, about 1.0 pL, about 1.5 pL, about 2.0 pL, about 3.0 pL, about 4.0 pL, about 5.0 pL, about 6.0 pL, about 7.0 pL, about 8.0 pL, about 9.0 pL, about 10 pL, about 11 pL, about 12 pL, about 13 pL, about 14 pL, about 15 pL, about 16 pL, about 17 pL, about 18 pL, about 19 pL, about 20 pL, about 21 pL, about 22 pL, about 23 pL, about 24 pL, about 25 pL, about 30 pL, about 40 pL, about 50 pL, about 60 pL, about 70 pL, about 80 pL, about 90 pL, or about 100 pL.
  • about 40 pL about 50 pL, about
  • droplet size distribution e.g., uniformity
  • sub-micron e.g., nano
  • uniformity e.g., uniformity
  • polydisperse particles e.g., droplets
  • the process of "break-off and jetting of the droplet from a nozzle may be at least in part determined by, or otherwise influenced by interplay of a number of factors, including the interfacial tension and the viscosity of the liquid ink, among other factors. This, in conjunction with the nozzle characteristic of the printer, in turn determines the size of the droplets that breaks off and to be deposited onto a substrate. Moreover, interactions between a bio-ink and a substrate (e.g., charge interactions) also affects the behavior.
  • the term "uniform” or “uniformity” refers to a composition characterized by a plurality of units of similar features with respect to a parameter (such as size, e.g., volume and diameter). The less the degree of deviation with respect to a parameter being measured, the greater the degree of uniformity within the composition.
  • dots of a bio-ink described herein are uniform in that liquid ink droplets deposited for printing show a narrow size distribution such that a majority of droplets within a single printing run fall within a specified range of volumes.
  • At least 50% of droplets have volumes within a specified range, wherein the specified range may be between about 1.0 pL and 20 pL. In some embodiments, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%), at least 95% or greater number of droplets within a single printing run have volumes within a specified range. The specified range may be between about 10 pL and about 20 pL. In some embodiments, provided aqueous bio-inks have a useful viscosity range of about 5-15 centipoise at jetting temperature.
  • provided aqueous bio-inks have a useful viscosity range of about 8-14 centipoise, e.g., about 8-13 centipoise, about 7-13 centipoise, about 6-12 centipoise, about 6-11 centipoise, about 7-12 centipoise, about 9-13 centipoise, about 10-13 centipoise, about 10-12 centipoise, for example, about 5 centipoise, about 6 centipoise, about 7 centipoise, about 8 centipoise, about 9 centipoise, about 10 centipoise, about 11 centipoise, about 12 centipoise, about 13 centipoise, about 14 centipoise, about 15 centipoise at jetting temperature.
  • provided aqueous bio-inks have a useful surface tension range of about 20-50 dynes/cm at jetting temperature. In some embodiments, provided aqueous bio-inks have a useful surface tension range of about 22- 48 dynes/cm, about 23-47 dynes/cm, about 24-46 dynes/cm, about 25-47 dynes/cm, about 26-46 dynes/cm, about 27-45 dynes/cm, 28-44 dynes/cm, for example, about 28 dynes/cm, about 29 dynes/cm, about 30 dynes/cm, about 31 dynes/cm, about 32 dynes/cm, about 33 dynes/cm, about 34 dynes/cm, about 35 dynes/cm, about 36 dynes/cm, about 37 dynes/cm, about
  • aqueous bio-inks exhibit low volatility, such that such bio-inks preferably have boiling point higher than 100 °C, e.g., about 100 °C, 101 °C, 102 °C, 103 °C, 104 °C, 105 °C, 106 °C, 107 °C, 108 °C, 109 °C, 110 °C, 111 °C, 112 °C, 113 °C, 114 °C, 115 °C, 116 °C, 117 °C, 118 °C, 119 °C, 120 °C, 121 °C, 122 °C, 123 °C, 124 °C, 125 °C, 126 °C, 127 °C, 128 °C, 129 °C, 130 °C, or greater.
  • aqueous bio-inks have specific gravity greater than 1.0.
  • aqueous bio-ink compositions have a useful pH range of between about 4 and 9, e.g., about pH 4.0, about pH 4.5, about H 5.0, about pH 5.5, about pH 6.0, about pH 6.5, about pH 7.0, about pH 7.5, about pH 8.0, about pH 8.5, about pH 9.0.
  • a buffer component may be added to such ink compositions to maintain the pH level in the ink.
  • buffering salt components may optionally comprise between about 0.1-0.5% (by weight) of bio- ink compositions.
  • structural proteins particularly suitable for formulating as a bio-ink are below 200 kDa, preferably below 150 kDa.
  • structural proteins (or fragments thereof) particularly suitable for formulating as a bio-ink have molecular weight ranging between about 3.5 kDa and about 120 kDa, e.g., about 3.5-110 kDa, about 3.5- 100 kDa, about 3.5-90 kDa, about 3.5-80 kDa, about 3.5-70 kDa, about 3.5-60 kDa, about 3.5-50 kDa, about 3.5-40 kDa, about 3.5-35 kDa, about 3.5-30 kDa, about 3.5-25 kDa, about 3.5-20 kDa, about 50-120 kDa, about 60-120 kDa, about 70-120 kDa, about 80-120 kDa, about 90-120 kDa.
  • such structural protein may be a full-length (e.g., wild type) structural protein having a molecular weight falling within any of the ranges shown above.
  • such structural protein may be so-called "low molecular weight protein," i.e., corresponding to reduced size fragments of a full-length counterpart, for example fragments of the full-length counterpart.
  • a silk fibroin ink composition where silk fibroin is used as a structural protein for a bio-ink, no more than 15% of the total number of silk fibroin fragments in a silk fibroin ink composition has a molecular weight exceeding 200 kDa, and at least 50% of the total number of the silk fibroin fragments in the population has a molecular weight within a specified range, wherein the specified range is between about 3.5 kDa and about 120 kDa.
  • Low molecular weight silk fibroin is described in detail in U.S. provisional application 61/883,732, entitled "LOW MOLECULAR WEIGHT SILK FIBROIN AND USES THEREOF," the entire contents of which are incorporated herein by reference.
  • consistency of a bio-ink may be further enhanced by selectively enriching certain range or ranges of fragment size (molecular weight) in a preparation.
  • a step of filtration may be included during the preparation of such an ink composition.
  • filters with a known cut-off range such as 0.2 ⁇
  • protein solution may be further processed, including extended heating and/or high pressure treatment, in order to promote fragmentation of large structural proteins.
  • an aqueous protein ink solution described herein may be heated (such as by boiling at atmospheric pressure) during the process of protein preparation for a period of time, e.g., for about 10 minutes, about 15 minutes, about 20 minutes, about 30 minutes, about 40 minutes, about 45 minutes, about 50 minutes, about 60 minutes, about 70 minutes, about 80 minutes, about 90 minutes, about 100 minutes, about 110 minutes, about 120 minutes, or longer.
  • such protein solution may be heated or boiled at an elevated temperature.
  • the protein solution can be heated or boiled at about 101.0°C, at about 101.5°C, at about 102.0°C, at about 102.5°C, at about 103.0°C, at about 103.5°C, at about 104.0°C, at about 104.5°C, at about 105.0°C, at about 105.5°C, at about 106.0°C, at about 106.5°C, at about 107.0°C, at about 107.5°C, at about 108.0°C, at about 108.5°C, at about 109.0°C, at about 109.5°C, at about 110.0°C, at about 110.5°C, at about 111.0°C, at about 111.5°C, at about 112.0°C, at about 112.5°C, at about 113.0°C, 113.5°C, at about 114.0°C, at about 114.5°C, at about 115.0°C, at about 115.5°C,
  • such elevated temperature can be achieved by carrying out at least portion of the heating process (e.g., boiling process) under pressure.
  • suitable pressure under which protein fragments described herein can be produced are typically between about 10-40 psi, e.g., about 11 psi, about 12 psi, about 13 psi, about 14 psi, about 15 psi, about 16 psi, about 17 psi, about 18 psi, about 19 psi, about 20 psi, about 21 psi, about 22 psi, about 23 psi, about 24 psi, about 25 psi, about 26 psi, about 27 psi, about 28 psi, about 29 psi, about 30 psi, about 31 psi, about 32 psi, about 33 psi, about 34 psi, about 35 psi, about 36 psi, about 37 psi,
  • protein solution may be further processed, including centrifugation.
  • provided aqueous bio-inks have low dissolved gas contents.
  • a step of degassing may be optionally performed prior to printing in order to enhance printing quality.
  • bio-inks comprising a structural protein described herein may contain a range of degrees/levels of beta- sheet crystallinity.
  • provided protein ink compositions may contain a beta-sheet content ranging between about 5% and 70%, e.g., about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65% or about 75%.
  • bio-inks biopolymer-based inks
  • a printed array comprises a substrate; and a plurality of dot units, wherein the plurality of dot units has a semi-solid or solid form, wherein each dot unit comprises a low molecular weight structural protein.
  • each dot unit on the substrate is between about 0.1-250 ⁇ in diameter.
  • a plurality of dot units is deposited upon a substrate in a predetermined spatial pattern to form a structure, e.g., 2D structures and 3D structures.
  • inkjet printers such as those described herein may be used to print biopolymer patterns, such as, for example, dots, signal line, and 2D patterns, on both hydrophilic and hydrophobic substrates.
  • the resolution of printing is affected by viscosity and surface tension of the biopolymer ink.
  • the resolution of pattern may depend on the roughness of the substrate and nozzle size of the printer.
  • An example printer that provides a lOpl size nozzle to make patterns produces a drop size around 25 ⁇ and the width of a printed line which is around 40um on the hydrophilic substrates.
  • a signal layer line will give the interface between dots, and a 2D pattern presents interface between lines.
  • the voltage is a function of drop size and drop velocity. So the voltage setting depends on the desired height level of the nozzle above the substrate and the desired drop size to be printed. However, with insufficient voltage (in some examples, voltage level below 15 V), the biopolymer ink will not come out due to the surface tension of biopolymer ink. Higher voltage settings, on the other hand, increase the volume of the drop.
  • FIG. 21 shows biopolymer lines on a silicon wafer under 15v, 20V and 25v voltage printing, with the width of the biopolymer lines being 65 ⁇ , ⁇ , and 1 ⁇ . As shown, high voltage printing gives greater- width lines due to increasing the drop volume.
  • a purging process may be performed, which applies air pressure to the outside of a fluid bag to force fluid through the entire fluid path and out all nozzles, as shown in the waveform of FIG. 22. After the purging process, air in the chamber is forced out of the nozzles, and ensures ink wets the nozzle to start printing.
  • a blotting process may be provided to absorb biopolymer ink in close proximity to the nozzle plate. After the blotting process, the excess biopolymer ink, which may cause misdirected firing, is removed.
  • a spitting process may protect the nozzle from clogging.
  • the spitting process provides for ejection of some drops ink from the chamber. This allows the fresh biopolymer drops to reach the meniscus to replace the previous one from the prior drop.
  • FIG. 23 shows a biopolymer line on acrylic with 25v and one nozzle printing, and provides a 40 ⁇ width biopolymer line.
  • FIG. 24 shows a biopolymer line with a 240 ⁇ - although still under 25 v printing, the width of the line is substantially increased in comparison to the pattern of FIG. 23, because of printing by seven nozzles as opposed to one.
  • FIG. 25 shows the drops from lOpL nozzles, and the voltage value set at 23V, with jetting frequency at 5 KHz.
  • the uniform drops from the nozzle show stable performance. There are no misdirected nozzles which means that biopolymer solution jetting smooth without bubbles under the high frequency oscillating system. All of the sixteen nozzles in this example work well for at least 8 hours which means the high temperature biopolymer will not clog the 20 ⁇ diameter nozzle.
  • FIG. 26 and FIG. 27 show biopolymer dots printed on silicon wafer and acrylic, respectively.
  • This example utilizes 1 nozzle and 1 -layer printing, the voltage value is 15v and the jetting frequency is 1 KHz.
  • the size of dots is 40 ⁇ on silicon wafer (FIG. 26) and 30 ⁇ on acrylic (FIG. 27).
  • FIG. 28 shows biopolymer lines which are printed with one nozzle and 15v on the silicon wafer.
  • FIG. 29 shows the SEM image of this one-layer printing.
  • One-layer printing is clear without any interface between drops. Comparing one-layer printing with three-layer printing, one-layer patterns are more uniform and the edge of line is cleaner. A rough edge is present in this example on three-layers printing (FIG. 30), because the upper layer fluid causes capillary instability when the upper layers of biopolymer are printed.
  • FIG. 31 shows the first line as being wider than the other four lines, because the alignment of first line is not as good as the other four lines.
  • FIG. 32 shows serious capillary instability in a twenty-layer pattern, so multiple-layer printing may be best suited, in some examples, for low resolution patterns.
  • the method for printing multiple layer lines and cross lines is different.
  • the substrate is fixed during printing and the direction of printing among multiple layer lines is the same.
  • the substrate is rotated by 90 degree C after first layer printing, and then the second layer printing is performed. As such, the direction of the two layers is different.
  • FIGS. 33 to 35 indicate capillary instability between two layers, and the edge of pattern shows a clean gradual capillary instability process.
  • a one-layer square pattern shows an interface between lines. As shown in the example of FIG. 36, there is less than 1 ⁇ width overlap between two lines. After applying a laser point to the pattern, a diffraction grating pattern shows on the wall due to the 1 ⁇ overlap, as shown in FIG. 37. However, the overlap part of the pattern disappears after printing the second layer pattern. As such, the multiple layers give a smooth finish pattern (FIGS. 38 and 39).
  • Biopolymer film is easily dissolved in water. However it will not dissolve after alcohol annealing due to the formation of ⁇ sheet.
  • a printer may be used to make a ⁇ sheet pattern. To do so, the printing pattern is set to do a 2-hour vacuum annealing. It turns out that, in some examples, the patterns tend to spread out, as shown in FIG. 40, which shows the biopolymer pattern before annealing and after annealing.
  • Biopolymers such as, for example, silk, provide a biologically favorable environment allowing them to entrain various biological and chemical dopants and maintain their
  • biopolymer solution examples include food color biopolymer, high refractive index biopolymer, and pure biopolymer (e.g., pure silk), and then printed with a number of nozzles.
  • FIGS. 41 to 43 show the thickness of patterns are increased by the number printing layer.
  • the thinnest pattern in this example is less than lOOnm created by a one-layer food color biopolymer pattern.
  • the thickest pattern is pure biopolymer pattern due to highest percentage biopolymer in the solution.
  • the printable substrates for biopolymer ink may include, for example, paper, glass, silicon, metals, cloth textiles, and plastics. Such substrates can be divided into two groups which are hydrophobic substrates and hydrophihc substrates. The drop size on hydrophobic substrate is smaller due to high surface energy.
  • the width of biopolymer lines from FIG. 28 is similar with respect to the biopolymer lines from FIG. 45. However, the two patterns are supplied by different voltages. Biopolymer patterns on silicon have slightly larger voltage values.
  • a biopolymer such as, for example, Silk fibroin is shown to be effective material and matrix that can maintain the functionalities of dopants. Therefore, choosing the appropriate dopants (including both physical dopants, e.g. metallic nanoparticles, laser dyes, quantum dots, etc., and biochemical dopants, e.g., cells, enzymes, bacterium, etc.) and mixing them into silk fibroin solution or other biopolymer solution as the ink is an advantageous way to directly print functional devices using an inkjet printer.
  • a series of functional biopolymer devices are described as examples.
  • biopolymers provide a biologically favorable environment allowing them to entrain various biological and chemical dopants and maintain their functionality.
  • Biopolymer films have been doped with gold nanoparticles such that they resonantly absorb incident light and convert the light to heat, which may used as, for example, a biocompatible thermal therapy for in vivo medical applications such as killing of tumor tissue and bacteria.
  • the preparation of gold nanoparticle biopolymer ink includes the production of the print grade biopolymer film (e.g., silk fibroin solution) and synthesis of gold nanoparticles, followed by a simple mixing of the two in solution with a certain ratio that is determined by application.
  • silk fibroin solution e.g., silk fibroin solution
  • pre-cut Bombyx mori cocoon pieces are boiled in a 0.02 M Na 2 C0 3 solution for 2 hours to remove sericin, and boiled silk fibers are dried overnight and then dissolved in a 9.3 M LiBr at 60 degree C for 4 hours.
  • the lithium bromide salt is then removed from the silk solution through a water-based dialysis process.
  • the gold nanoparticle solution is prepared by adding 20 mL 1% a 3 C 6 H507 into 200 mL boiled 1.0 mM HAuCl 4 , followed by continuously heating for 10 minutes until the solution has turned deep red. Then the gold nanoparticle solution is carefully added into the silk solution with gentle agitation for uniform dispersion and is ready for printing after being filtered, e.g., against a 0.2 micron filter.
  • Table 5.1 provides the main parameters for printing and the printing result is shown in FIG. 47.
  • the printed Au-NPs doped biopolymer device shows enhanced plasmatic absorption of green light (FIG. 48), resulting in a temperature increase of ⁇ 15 degree s with an irradiance of ⁇ 0.25 W/cm .
  • the heating effects could be further improved and optimized by adjusting the Au-NPs concentration and layers of the printed structures, which could be potentially used for light- mediated patterned heating treatments.
  • ELISA immuosorbent assay test
  • ELISA is a widely used test to identify certain substances using antibodies and the colorimetric change as the sensing/diagnostic mechanism.
  • the enzymes used in ELISA tests need to be stored at low temperature for maintaining the bioactivities. It has been shown that biopolymer can help to maintain the functionalities of the doped enzyme at room temperatures without fridge-storage. Therefore, directly printing of enzyme-doped biopolymer patterns (in a precise way) is an advantageous mechanism for applications such as, for example, rapid and low volume screening tests, food allergens, and toxicology applications, as shown in FIG. 49. Inkjet printing of antibiotics doped biopolymer patterns
  • antibiotics are important for effective infectious disease containment and curing. However, most, if not all, current antibiotics need to be maintained within a specific refrigeration temperature range due to their temperature sensitivity.
  • Silk fibroin as an example, has been proven to be a biologically friendly protein polymer. Recently, researchers found that silk was capable of stabilizing labile antibiotics (in the form of films) even at temperatures up to 60 degree C over more than 6 months. Direct inkjet printing of antibiotics-doped biopolymer by mixing penicillin solution of various concentration levels with purified biopolymer solution prepared as previously described may be provided.
  • the pattern is printed after bacterial overnight growth, as provided by method two, below. There is an arrow in the in the Petri dish after 9 hours incubation (FIG. 51).
  • biopolymers are used to construct edible food sensors as a green and edible material that is extracted and purified from domesticated silkworm cocoons.
  • Plain biopolymer solution i.e. non-doped biopolymer solution
  • Color additive imparts color when added to food or drink, and is used widely both in commercial food production and in domestic cooking.
  • biopolymer inks e.g., for direct inkjet printing.
  • patterns may be printed on textile silk which carries a basic color (light yellow).
  • multiple-layer printing may be beneficial, because the color of textile silk is darker than a blank paper. After seven layers of printing, the pattern is clear and beautiful, as shown in FIG. 52.
  • the colored silk patterns remain in their original patterns after 2 hours of vacuum annealing. The patterns also survive a dry cleaning process, as shown in FIG. 53.
  • Multiple-color biopolymer printing may benefit from an alignment process, because the printer in accordance with some examples, loads one cartridge with one color at a time, as shown in FIG. 54.
  • there are four steps of alignment including multiple-layer alignment, cartridge, voltage alignment, and nozzle alignment.
  • Multilayer alignment one color for each layer of printing
  • Cartridge alignment set drop offset before every layer printing
  • Nozzle alignment using the same nozzles for every layer printing (number of nozzles determines line width).
  • biopolymer inks may be prepared by choosing appropriate dopants and mixing with the biopolymer solution (e.g., purified silk fibroin solution), and printed.
  • a set of operating parameters may be optimized for each individual biopolymer ink (including, for example, gold nanoparticle biopolymer ink, enzyme-doped biopolymer ink, high refractive index biopolymer ink, and antibacterial biopolymer ink) to improve the performance for specific applications.
  • Both single layer and multiple-layer printing may be carried out, with advantageous resolutions (e.g., a resolution of 25 microns).
  • bio-inks biopolymer-based inks
  • a printed array comprises a substrate; and a plurality of dot units, wherein the plurality of dot units has a semi-solid or solid form, wherein each dot unit comprises a low molecular weight structural protein.
  • each dot unit on the substrate is between about 0.1 -250 ⁇ in diameter.
  • a plurality of dot units is deposited upon a substrate in a predetermined spatial pattern to form a structure, e.g., 2D structures and 3D structures.
  • printed forms of biopolymer-based inks prepared in accordance with the disclosure of the present application have a resolution of between about 50-20,000 dpi, e.g., about 100 dpi, about 200 dpi, about 300 dpi, about 400 dpi, about 500 dpi, about 600 dpi, about 700 dpi, about 800 dpi, about 900 dpi, about 1000 dpi, about 1100 dpi, about 1200 dpi, about 1500 dpi, about 2000 dpi, about 2500 dpi, about 3000 dpi, about 3500 dpi, about 4000 dpi, about 4500 dpi, about 5000 dpi, about 5500 dpi, about 6000 dpi, about 6500 dpi, about 7000 dpi, about 7500 dpi, about 8000 dpi, about 8500 dpi, about 9000
  • substrates may be suitable for use in printing a bio-ink described herein.
  • Such printable substrates using bio-inks are limitless, simply depending on the available inkjet printers.
  • Non4imiting examples of useful substrates include, but are not limited to: papers, polyimide, polyethylene, natural fabric, synthetic fabric, metals, liquid crystal polymer, palladium, glass and other insulators, silicon and other semiconductors, metals, cloth textiles and fabrics, plastics, biological substrates, such as cells and tissues, protein- or biopolymer-based substrates (e.g., agarose, collagen, gelatin, etc.), and any combinations thereof.
  • provided bio-inks can be printed on substrates that generally are of a flexible material, such as a flexible polymer film or paper, such as wax paper or non-wax substrates.
  • suitable substrates include releasable substrates, such as a label release grade or other polymer coated paper, as is known in the art (e.g., see 6,939,576).
  • substrate also can be or include a non-silicone release layer.
  • Such substrate also can be a plastic or polymer film, such as any one of an acrylic-based film, a polyamide-based film, a polyester-based film, a polyolefm-based film such as polyethylene and polypropylene, a polyethylene naphthylene-based film, a polyethylene terephthalate-based film, a polyurethane -based film or a PVC-based film, or a combination thereof.
  • a plastic or polymer film such as any one of an acrylic-based film, a polyamide-based film, a polyester-based film, a polyolefm-based film such as polyethylene and polypropylene, a polyethylene naphthylene-based film, a polyethylene terephthalate-based film, a polyurethane -based film or a PVC-based film, or a combination thereof.
  • inkjet printing can be employed for printing patterns of bio-inks, such as silk fibroin inks (with or without dopants).
  • bio-inks such as silk fibroin inks (with or without dopants).
  • the printable patterns (e.g., structures) using bio-inks are limitless, simply depending on the available inkjet printers.
  • the printable patterns (e.g., structures) include, but are not limited to regular and irregular patterns, such as lines, curves, dots, solids, and any combinations thereof.
  • Each pattern or structure to be printed is formed from a plurality of small "dots" each of which is generated from a liquid droplet of a bio-ink deposited onto the substrate.
  • Such patterns can be either one layer of dot prints or multilayer of prints (e.g., serial printing), depending on the intended applications.
  • Each layer in the multilayer prints can be overlapping on top of each other for thicker patterns or cross with other layers for complicated patterns.
  • serial printing can be performed to fabricate a 3D structure.
  • bio-inks comprising a structural protein described herein may contain a range of degrees/levels of beta- sheet crystallinity.
  • provided protein ink compositions may contain a beta-sheet content ranging between about 5% and 70%, e.g., about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65% or about 75%.
  • a conformational change can be induced in such structural protein or low molecular weight fragments thereof to control or tune the solubility of the protein-based structure printed on a substrate.
  • the conformational change can induce the protein at least partially insoluble.
  • the induced conformational change alters the crystallinity of the protein, e.g., beta-sheet crystallinity.
  • the conformational change may be induced by any methods known in the art, including, but not limited to, alcohol immersion (e.g., ethanol, methanol), water annealing, shear stress, ultrasound (e.g., by sonication), pH reduction (e.g., pH titration and/or exposure to an electric field) and any combinations thereof.
  • the conformational change can be induced by one or more methods, including but not limited to, controlled slow drying (Lu et al, Biomacromolecules 2009, 10, 1032); water annealing (Jin et al, 15 Adv. Funct. Mats. 2005, 15, 1241; Hu et al.
  • EDC carbodiimide
  • the conformation of certain structural proteins in a bio-ink, including silk fibroin may be altered by water annealing.
  • TCWVA physical temperature-controlled water vapor annealing
  • the relative degree of crystallinity can be controlled, ranging from a low beta-sheet content using conditions at 4 °C (a helix dominated silk I structure), to higher beta-sheet content of 60% crystallinity at 100 °C ( ⁇ -sheet dominated silk II structure).
  • alteration in the conformation of certain structural proteins may be induced by immersing in alcohol or organic solvent, e.g., methanol, ethanol, propanol, acetone, etc.
  • the alcohol concentration can be at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90% or 100%). In some embodiment, alcohol concentration is 100%).
  • the alteration in the conformation is by immersing in a solvent, the protein composition can be washed, e.g., with solvent/water gradient to remove any of the residual solvent that is used for the immersion. The washing step can be repeated one, e.g., one, two, three, four, five, or more times.
  • the alteration in the conformation of certain structural proteins can be induced with shear stress.
  • the shear stress can be applied, for example, by passing a structural protein composition through a needle.
  • Other methods of inducing conformational changes include applying an electric field, applying pressure, and/or changing the salt concentration.
  • the treatment time for inducing the conformational change can be any period of time to provide a desired degree of beta- sheet crystallinity content.
  • the treatment time can range from about 1 hour to about 12 hours, from about 1 hour to about 6 hours, from about 1 hour to about 5 hours, from about 1 hour to about 4 hours, or from about 1 hour to about 3 hours.
  • the sintering time can range from about 2 hours to about 4 hours or from 2.5 hours to about 3.5 hours.
  • treatment time can range from minutes to hours.
  • immersion in the solvent can be for a period of at least about 15 minutes, at least about 30 minutes, at least about 1 hour, at least about 2 hours, at least 3 hours, at least about 6 hours, at least about 18 hours, at least about 12 hours, at least about 1 day, at least about 2 days, at least about 3 days, at least about 4 days, at least about 5 days, at least about 6 days, at least about 7 days, at least about 8 days, at least about 9 days, at least about 10 days, at least about 11 days, at least about 12 days, at least about 13 days, or at least about 14 days.
  • immersion in the solvent can be for a period of about 12 hours to about seven days, about 1 day to about 6 days, about 2 to about 5 days, or about 3 to about 4 days.
  • structural proteins such as silk fibroin
  • structural proteins may comprise a beta-sheet crystallinity content of at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%), at least about 70%, at least about 80%, or at least about 90%>.
  • Device e.g., printers
  • inkjet printers have grown in popularity and performance - actually, inkjet printers are by far the most popular since their introduction in the latter half of the 1980s.
  • laser printers which use dry ink, also known as toner, static electricity, and heat to print
  • inkjet printers use liquid inks and nozzles (usually multiple nozzles needed) to spray drops of ink directly onto the substrates.
  • a typical inkjet printer includes: a) print head - that contains a series of nozzles that are used to spray the ink drops; b) ink cartridge - that contains the ink; c) stepper motor - that moves the print head back and forth across the substrate.
  • piezoelectric nozzle techniques for precision printing. Such techniques use piezo crystals that vibrate when they receive a very small electric charge. When the crystal vibrates inward and outward, it pulls and forces a tiny amount of ink and sprays it out of the nozzle.
  • the inkjet printer may be, for example, a commercial inkjet printer, e.g., a FUJIFILM Dimatix Materials Printer DMP-2800.
  • the illustrated printer uses piezoelectric inkjet technology and MEMS fabrication processes (for cartridges, nozzles and etc.).
  • the printer includes a base, a print cartridge, a maintenance station blotting pad, a platen, a drop watcher, and a lid.
  • the printer works, in this example, with a maximum printable area of A4 size substrate (8x11 inch) with a disposable (but reusable with certain modifications/tweaks) piezo inkjet cartridge.
  • the maximum height of printable substrate is up to 25 mm in the illustrated example.
  • the printer also has the ability to heat up the substrate up to 60 degrees C.
  • there is a fiducially camera available allowing real time watching the formation of the drop as it is ejected from the nozzle.
  • the printer may serve as a convenient laboratory tool that enables users (e.g., students, researchers, and engineers) to evaluate the use of specific inks (e.g., silk fibroin solution in accordance with example embodiments) for new and proof of principle technology development with extensive flexibilities to optimize process parameters for user oriented applications.
  • users e.g., students, researchers, and engineers
  • specific inks e.g., silk fibroin solution in accordance with example embodiments
  • Printer-compatible substrates may include, for example: paper, Kapton (i.e. polyimide), poyethylene (PET), fabrics (such as, for example, cotton, nylon, polyester), metals (such as, for example, aluminum foil, copper foil, stainless steel foil and etc.), liquid crystal polymer, palladium, and glass.
  • Kapton i.e. polyimide
  • PET poyethylene
  • fabrics such as, for example, cotton, nylon, polyester
  • metals such as, for example, aluminum foil, copper foil, stainless steel foil and etc.
  • liquid crystal polymer palladium, and glass.
  • Printer-compatible fluids/inks may include, for example: conductive silvers, conductive inorganics (e.g., non silver ink, such as ITO inks) , conductive organics (such as OLED), single wall carbon nanotubes (SWCNTs), insulators, polyimides, photoresists, resins, and UV curable inks.
  • conductive silvers e.g., non silver ink, such as ITO inks
  • conductive organics such as OLED
  • SWCNTs single wall carbon nanotubes
  • insulators e.g., polyimides, photoresists, resins, and UV curable inks.
  • inkjet printer for conductive printing is rapid printing of RFID tags.
  • this is a rather challenging endeavor since precise control of the desired conductivity and pattern designs (on non-perfect substrates, for example, on non-glossy rough papers).
  • conductive inkjet printing for RF applications jets the single conductive ink droplet from the nozzle to a predefined position (usually controlled by, for example computer and a precise motor stepper).
  • Silver nano-particle inks are selected and commonly used for good metal conductivity.
  • a sintering process either by applying heat or UV exposure (to remove excess solvent and to remove material impurities) is usually needed, which also enhance the bond strength between the ink and the as-printed substrate.
  • an immediate sintering process may be essential, because the biopolymer ink may begin to oxidize, which would reduce the efficiency of conductivity of the metallic patterns.
  • FIG. 8 there are, in the illustrated structure, gaps between printed silver nanoparticles after printing, resulting in a poor connection and therefore lack of sufficient conductivity.
  • the particles After a period, e.g., 15 minutes, of a heating/curing process, the particles begin to aggregate and gaps start to diminish, which forms a continuous metal film and guarantees a good conductor, which determines the performance of printed electric devices such as, for example, an RFID tag as shown in Fig. 9.
  • the simulated and measured intensity over frequency of an example embodiment in accordance with FIG. 9 is shown in FIG. 10. As shown in the graph, this example has a working frequency of 2 GHz, although example embodiments may be configured to have any suitable frequency range.
  • bioprinting which requires micro- level, and in many cases, nano-level, liquid manipulation.
  • Typical applications may include, for example, micro-dosing, biochemical surface patterning and modification, tissue engineering and importantly the direct placement of living cells, DNA arrays, and proteomics. Questions have been raised on the influence of mechanical forces and relatively intense electric field during the inkjet process on cells and some research reports show that although some cell death may occur, surviving cells recover rapidly and seem to behave normally, as shown in FIG. 11.
  • materials printers are used to directly print regenerated silk fibroin protein.
  • the printers may be able, in some implementations, to create patterns and load BMP patterns over any suitable area (e.g., an area of about 200x300mm).
  • the printers may allow substrates having any suitable dimensions, (e.g., substrates up to 25mm thick or much thicker or thinner substrates) and may have an adjustable Z height.
  • the materials printers may have any suitable number of jetting nozzles, e.g., piezo-based jetting nozzles.
  • a materials printer may have a single nozzle or a plurality of any desired number of nozzles. In some embodiments, between 8 and 32 nozzles are provided. For example, some embodiments have 16 jetting nozzles. Where a plurality of such nozzles are provided, the nozzles may be arranged with any suitable spacing, which may be regular or irregular. For example, the nozzles may be spaced from each at a spacing that is between 30 ⁇ and 500 ⁇ , between 50 ⁇ and 400 ⁇ , between 150 ⁇ and 350 ⁇ , or between 200 ⁇ and 300 ⁇ , e.g, at 254 ⁇ spacing.
  • the nozzle or nozzles may be provided in connection with a fillable cartridge.
  • a method in which the biopolymer base (e.g., silk fibroin protein) is regenerated as the ink to match specific fluid requirement of the printer.
  • the printed biopolymer e.g., silk protein
  • the printed biopolymer may be biocompatible and can be further functionalized by mixing the biopolymer ink with appropriate dopants (including, for example, organic and/or inorganic dopants) for specific applications.
  • the printer may serve, for example, as a powerful laboratory tool, and may have capabilities to allow users to optimize process parameters, such as, for example, nozzle voltage, substrate height, and wave form.
  • the printer may, in some embodiments, provide multi-layer printing and allow an alignment process when using multiple cartridges and matching the origin point on the substrate.
  • the printer operates according to a method including creating a pattern, loading ink, and setting printing permanents.
  • a printer may be utilized in an example method that includes creating a pattern, loading ink, and setting printing permanents.
  • the printer may include a processor running software and that accepts pattern files and/or provides a pattern creation and editing software interface to allow users to create and/or edit patterns.
  • the pattern creation and editing software allows the user to modify a pattern of drops for printing, which may be useful for some fine and small scale patterns, for example, patterns illustrated in FIG. 12.
  • creating a complex structure pattern for printing may be very time consuming. For patterns such as illustrated in FIG. 13, a transformation to a pattern design file format may first be required, followed by importation into the pattern design software.
  • a user may first make a high resolution original file before transforming the file into the file format of the pattern design and editing software, because some such software only allows importation of monochrome Bitmap files which can be a low resolution file.
  • a user may select an option titled Pattern Editor (Bitmap images) from the main software window and choose a drop space size which depends on the ink and substrate before importing the Bitmap file. It may be beneficial for the user to double check the final size of the pattern to minimize the risk of error. If the final size is not in accordance with the user's expectation, the user may adjust the final size by changing the pattern size in the Bitmap file, then reloading the pattern.
  • the pattern may be repeated by controlling a placement number.
  • the user may select an option in the software, e.g., in a main windows of the software, and select an option indicated as Pattern Edition. This allows the user to create a pattern by entering dimensions in a Pattern Block Drop Positions field. Alternatively, the user may draw a feature through a corresponding software window. Before creating the pattern, the user may wish to choose the size of drop spacing which is the center to center distance from one drop to the next. For a normal biopolymer drop (e.g., a silk drop) the drop spacing may be, for example, about 25 ⁇ on a hydrophilic surface, such as, for example, a silicon wafer.
  • a hydrophilic surface such as, for example, a silicon wafer.
  • the ink used to fill into the cartridge may need go through a filter first.
  • a filter first For example, for a 26 ⁇ nozzle and a drop volume of 10 pL, the ink may pass through a 0.22 ⁇ filter first.
  • the nozzle may easy be clogged by particle sizes larger than 0.22 ⁇ .
  • the user may change the clean pad for new ink to avoid contamination by other chemicals.
  • the user may select the pattern the use wishes to print from the software.
  • the system may automatically calculate the cartridge mounting angle determined by drop spacing specified in the pattern. Table 2.1 shows the relation of saber angle, resolution, and drop spacing.
  • the user may select a drop watch button and the system may move the cartridge to the right side of the platen, positioning the nozzles over the drop watcher camera system.
  • the user may first select the range of nozzles the user wishes to jet the pattern.
  • the user may modify the nozzles to uniform performance by adjusting voltage of those nozzle as being monitored by camera.
  • Another potentially important parameter the user may wish to set up carefully is the cartridge print height according to the substrate thickness. If the substrate thickness is, for example, less than 0.5mm, the printable range may be 210mm*315mm. If the substrate thickness is, for example, from 0.5mm to 25mm, the printable range may be 210mm*260mm.
  • the repeatability distance may be, for example, ⁇ 25 ⁇ .
  • the last step before printing may be an alignment process through a fiducial camera tool, e.g., via a tools menu in the software window.
  • the user may calibrate the position of a new cartridge or head angle by setting the drop offset to automatic or manual, e.g., from the tools menu.
  • the user may set the printing origin point and reference point for multiple-layer printing.
  • the main parameters may include, for example, nozzle voltage, nozzle temperature, meniscus set point, cleaning cycles, and waveform.
  • the user may click on an edition button the cartridge setting box of the software.
  • the voltage of each nozzle may be individually adjusted, as shown in FIG 14. Increasing voltage increases drop volume and jetting velocity.
  • a suitable velocity to be set is, for example, 7-9m/sec.
  • the user may make a selection in the cartridge settings of the software.
  • the user may lower the ink viscosity and surface tension by increasing nozzle temperature.
  • the printer may allow the user to adjust nozzle temperature in a range from, for example, 28 degree C to 70 degree C, as shown in FIG. 1 .
  • a good viscosity of printing ink is 10-12 centipoises and a good surface tension of printing ink is 28-44 dynes/cm, although other viscosities and surface tensions may be provided in example embodiments.
  • Meniscus vacuum is a negative pressure for keeping the meniscus at the edge of nozzle.
  • the user may change the value of meniscus vacuum depending on the viscosity and surface tension of the ink.
  • the typical meniscus vacuum value of water is 4 inches. If the meniscus vacuum number is not correct, the performance of ink may be affected with high frequency.
  • the user may choose the number of nozzles from which to print, and the system may automatically compensate for the number of nozzles used but the nozzles selected may only be one series of adjacent nozzles.
  • the printer has a drop watch camera which allows the user to monitor, in real time, the drop performance. In this way, the camera may assist the user to ensure that the nozzles chosen performance uniformly. Cleaning Cycles
  • a cleaning cycle table allows the user to set nozzle cleaning processes before, during, and after printing.
  • Setting cleaning cycle before printing may give a uniform start for every running of the printer.
  • Cleaning cycle may be especially important for some high viscosity applications, because setting cleaning cycle during printing may prevent the high viscosity ink from clogging.
  • Setting the cleaning cycle after printing may facilitate maintenance of the nozzles, as shown in FIG. 16.
  • the printer software may have any suitable wave fore, for example, a standard 4-step waveform which is good for normal ink (e.g., ink having a viscosity of 11-12 centipoises and a surface tension of 28-32 dynes/cm.
  • the 4 steps may include start, phase 1, phase 2, and phase 3.
  • the basic concept for these 4 steps is use a bias voltage to control piezo actuation to suck a drop of ink and jet it with a controlled velocity.
  • the nozzle voltage is set to a 40% level and is held for 1 ⁇ 8.
  • the channel which is piezo basic slightly deflected and sucks some ink from cartridge starting to eject, as shown in FIG. 17.
  • the voltage level may be set to 0 and held for, e.g., 3.584 ⁇ or any other suitable period, e.g., a period in a range from 3 ⁇ to 4 ⁇ .
  • the voltage brings the piezo back to a neutral straight position with the chamber at its maximum volume.
  • the fluid is filled into chamber.
  • FIG. 18 shows the meniscus at the nozzle edge.
  • Phase 2 is a firing pulse , as shown in FIG. 19.
  • the steepness of the slope provides the energy for initial ejection and it is followed by a hold period.
  • the voltage increases to 100% level and is held for, e.g., 3.712 ⁇ or any other suitable period, e.g., a period in a range from 3 ⁇ to 4.5 ⁇ .
  • the chamber starts to jet a drop of ink.
  • the velocity of a drop can be calculated.
  • Phase 3 the last phase of the waveform, is a return to standby, as shown in FIG. 20.
  • the voltage level decreases to 70% and is hold it for, e.g., 3.392 ⁇ (or any other suitable period, e.g., a period in a range from 3 to 4 ⁇ ), which is intended to prevent the printed head from sucking air back in.
  • the voltage level is brought to 40% level and chamber back to the standby position.
  • Those parameters mentioned above may play an important role during printing. They may advantageously be checked every printing running according to the ink and material of substrate. Also ink condition may slightly change according to room temperature and humidity level.
  • the prepared silk fibroin inks can be filled into any types of liquid-reflllable based cartridge for commercial inkjet printers.
  • the lifetime of the inks depends on the usage and the storage conditions. In some embodiments, storage in a refrigerator at 4 degree C when finishing printing is recommended.
  • silk inks (with our without dopants) may be stored without refrigeration, such as at room temperature (between about 18-26°C) for an extended duration of time without significant loss of function.
  • High resolution depending on the specific model of the printer) can be achieved for printers with fine nozzle size and the access to control the nozzle operating performance (for example, firing voltage and waveform, cleaning cycle, printing temperature and etc.)
  • Biomaterials have evolved from inert, monolithic matter, into "bio-instructive", hybrid systems, with specific functionalities that are defined by correspondingly specific applications [1]. This approach limits the possibility to apply a single biomaterial widely by favoring the functionality dictated to meet stringent therapeutic requirements. Regulations that enforce the clinical use of biomaterials (e.g., FDA approval is not given to the biomaterial per se but to its specific application) have also contributed to the current high specialization of biomaterials. Under this approach, biomaterials are conceptualized as bio-high-tech materials, which are provided to the end-user in their refined state, as "ready-for-use” products. The present application challenges this viewpoint by developing the scientific underpinnings of a technology that provides the end-user with a unified "base biomaterial” or platform material, whose final utility can be easily and controllably defined at the end-users' site.
  • inkjet printing e.g., with personal printers
  • inkjet printing of bio-inks is provided as a platform.
  • inkjet printing of bio-inks can enable the fabrication of custom printable biomaterials for a variety of applications.
  • such platform is useful for optics, photonics, electronics, as well as therapeutics and sensing applications.
  • Non- limiting examples of enabled applications range from drug-doped printable inks that can preserve heat-sensitive biomacromolecules without refrigeration (elimination of the cold-chain), to functionalized silk ink libraries to be used for printable drug formulation or activation (elimination of user-induced error in drug reconstitution).
  • Another concept involves biological and environmental analysis on orthogonal printing of 'sensing' silk ink libraries.
  • a set of device designs to address applications ranging from drug delivery to biochemical analysis described herein is based at least on the following: (1) development of bio-inks, such as silk inks, that stabilize vaccines and integrate the vaccine reconstitution within the printing process; (2) bio-inks that topographically control the release of antibiotics; (3) bio-inks that allows for basic biochemical analysis of biological samples, including human tissues (e.g. blood, urine); and, (4) bio-inks that spatially control stem cell fate by a controlled release of custom- printed growth factors.
  • bio-inks such as silk inks
  • example embodiments of the invention described herein combine diverse, but highly complementary, technology that will generate foundational knowledge for both material design and material processing.
  • New insights may be given in silk fibroin polymorphism, providing new approaches for fibroin processing, fibroin phase transformation and fibroin interaction with several classes of bio functional macromolecules.
  • a new approach is needed for biomaterial design to enable a versatile technology that starts uses a common production platform (e.g., inkjet printing) yet covers a broad range of outcomes and applications.
  • the standard processes of fibroin regeneration has to be re-invented and tuned to achieve useful operation; new processing approaches are essential for use with practical inkjet systems through personal printers; new ways to stabilize fibroin solution are required to achieve useful operation.
  • Vaccines and antibiotics are important components of an effective infectious disease containment strategy; antibiotics represent a rescue measure while vaccination can be a primary mode of disease prevention.
  • antibiotics represent a rescue measure while vaccination can be a primary mode of disease prevention.
  • the use of vaccines and antibiotics is severely limited in the poorest countries where infectious diseases account for more than half of all deaths.
  • Due to temperature sensitivity, vaccine and antibiotic formulations must be maintained within a specific refrigeration temperature range. Because ambient temperatures in the developing world deviate significantly from refrigeration temperatures, the successful delivery of active vaccines and antibiotics depends on the cold chain system, a distribution network to maintain optimal cold temperatures during transport, storage, and handling. Cold chain requirements represent a major economic and logistical burden, particularly in lower resource settings, where refrigeration and electricity can be limited.
  • the cold chain alone can account for 80% of the financial cost of vaccination and is estimated to cost vaccine programs $200-300 million per year. Deficiencies in the process frequently occur even in industrialized countries. For temperature sensitive compounds like vaccines and antibiotics, maintaining the cold chain is critical for adequate bioactivity. Failures in the cold chain result in costly waste and the loss of nearly half of all global vaccines. Such failures can also result in the delivery of ineffective, sub-therapeutic doses. For antibiotics, this problem can be associated with the development of antibiotic-resistant strains, a major public health concern.
  • An AEFI is any adverse event that follows immunization that is believed to be caused by the immunization. Immunization can produce adverse events from the inherent properties of the vaccine (vaccine reaction), or some errors in the immunization process (programme error). Although rare in the developed countries, program errors are more frequent in the developing world, where non-sufficient structures limit and negatively influence the use of recommended immunization practices. Generally, these errors results from mistakes and/or accidents in vaccine preparation, handling, or administration and results from the poor conditions in which immunization is practiced. Examples of the common mistakes are inadequate shaking of the vaccine before use, errors in the reconstitution of vaccines before they are administered, contamination of vaccine or injection equipment, use of a drug instead of a vaccine or diluent, superficial injection, and use of frozen vaccine. Current applications of bioprinting
  • Bio-printing allows for the dispensation of pico-sized quantities of biomaterial solutions (such as protein solution, nucleic acid solution, etc.) to designated sample space with minimal waste, both of which are highly sought features in processing biological materials. What follows is a summary of exemplary applications, in which bio-printing is explored. Biosensors and immunoassay tests
  • a biosensor is an analytical device that uses antibodies, enzymes, nucleic acids, microorganisms, isolated cells, or other biologically derived systems as a sensing element. In terms of cost, very small quantities of material are required to make sensors, and inkjet deposition lends itself well to mass production, allowing for sensors in many applications to be treated as disposable.
  • Silk fibroin polymorphism overturns the general concept that structural protein with high molecular weight cannot be printed at high concentration. Under certain conditions, regenerated silk fibroin possesses the unique property of having a globular form. This allows for the on- demand extrusion of the solution through nozzle with a sub-micrometric diameter, mimicking the natural extrusion of silk solution. Unpublished work within our laboratory has developed a protocol to obtain printable silk inks to establish a set of functional silk-based inks.
  • Dedicated (FujiFilm Dimatix Materials Printer DMP-2800) and personal ⁇ e.g. Epson Artisan 1430 and Epson WorkForce 30) printers have been used to print functionalized fibroin- based inks.
  • the dedicated printer has been used to prove the concept of printing fibroin-based inks and to assess the different condition (e.g. process type, drop size) of the inkjet printing process.
  • the piezoelectric driven ejection of the drop has been preferred to the thermal one.
  • a droplet size in the range of 6-20 pi has been chosen. Within this range, in fact, it was possible to successfully print all the fibroin-based inks investigated.
  • Epson is the only commercial brand to offer piezoelectric inkjet technology.
  • Epson printers have a Variable Size Droplet Technology ® , that allows to choose between five pre-determined drop sizes (1.5 to 15 pi).
  • the substrate is part and parcel of the UP fibroin-based biomaterials.
  • the ink-substrate system may be considered either a hybrid (no separate interfaces between ink and substrate) or a composite (separate interfaces). This distinction may strongly influence the structural, functional, mechanical and biological properties of the deposited proteins.
  • different choices of substrates may tailor the properties of the end product.
  • silk-based UP substrates Plain paper is used both as a 'standard' substrate and as a substrate for colorimetric sensing applications.
  • Silk-based electrospun matrices are used for tissue engineering and therapeutics applications. Silicon wafers have been tested for
  • Tissue culture plastics are used for biological applications.
  • Microneedle-Silk-sheets may be used for vaccine delivery.
  • inkjet printable, SF-based biomaterial We have developed an unprecedentedly versatile, inkjet printable, SF-based biomaterial.
  • the possibility to ink-jet print SF may accompany the SF-induced preservation, stabilization, and controlled-release of biomacromolecules with the possibility to obtain a programmable topographic control of their release in the micro-scale.
  • SF may be successfully implemented to immobilize and stabilize sensing molecules and to drive their interface with electronics device.
  • SF has been preferred to other abundant biopolymers (e.g. collagen, chitosan and keratin) due to the properties of the solvated protein.
  • soluble collagen is only obtainable at pH ⁇ 4.0 (in the form of tropocollagen dimers or timers) and at low densities ( ⁇ 0.5 wt%)
  • chitosan can only be solubilized in acidic conditions, and keratin is expensively obtained in aqueous solution only at low concentration ( ⁇ 0.5wt%).
  • Silk ink design This fundamental material characterization will not only cope with the technological challenges involved in the UP process of stable macromolecules, but it will also open the door to their stabilization in silk solutions. This is a step towards therapeutic inkjet printing technology.
  • pH ionic strength, protein and salts concentration may be considered in order to tailor the viscosity and the surface tension of the silk solutions.
  • pH plays the major role in controlling the silk solution's viscosity.
  • pH ⁇ 3.5 the chains are reversibly aggregating in crystalline ⁇ -sheet crystals, forming a gel structure.
  • SF chains irreversibly degrade in small polypeptides.
  • An optimum pH range between 6-8 may be therefore targeted in the design of the silk-based inks.
  • EDTA, citric acids are also reported to cross-link SF chains, producing an increase in the viscosity and in the particle size.
  • the combined effects of these parameters on the micellar and liquid crystalline form of SF chains in liquid phase may be therefore investigated.
  • the morphological analysis of the SF solution may be accomplished with CryoTEM. The use of this technique to analyze regenerated silk solutions may provide a snapshot of the chain
  • Circular dichroism CD
  • dynamic light scattering DLS
  • Raman spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy may be used to monitor the effects of the aforementioned parameters on SF chain distribution, profile, orientation and structure.
  • ATR-FTIR attenuated total reflectance Fourier transform infrared
  • Viscosity and surface tension measurements may evaluate the efficacy of the proposed changes. With the exception of CryoTEM, all the instruments necessary to achieve a deep characterization of SF solution are available in house. Transmission electron microscopy may be carried out at the NSF-funded Harvard Center for Nanoscale System (CNS), as for previous studies.
  • CNS Harvard Center for Nanoscale System
  • hybridized silk inks with antibiotics (e.g., penicillin, neomycin, gentamycin, streptomycin, and tetracycline), vaccines (e.g., Merck M-M-R ® II - Measles, Mumps, and Rubella Virus Vaccine), enzymes (glucose oxidase) and growth factors (to control human mesenchymal stem cells (h-MSCs) fate toward osteogenic (ascorbic acid, ⁇ -glycerolphosphate and dexamethasone) and chondrogenic (IGF-1, TGF- ⁇ ) lineages.
  • antibiotics e.g., penicillin, neomycin, gentamycin, streptomycin, and tetracycline
  • vaccines e.g., Merck M-M-R ® II - Measles, Mumps, and Rubella Virus Vaccine
  • enzymes glucose oxidase
  • growth factors to control
  • the problem may be approached by hybridizing different amounts of any of the above mentioned macromolecule with the current fibroin standard solution for printing.
  • the analysis of the rheological properties of the solution together with the measurement of the particle size may then provide an indication of the printability of the hybrid inks. If the requirements to obtain a printable solution are not met (particularly due to the aggregation of SF chain in the solution to form particles >200nm), strategies such as the use of additives (e.g., divalent cations), changes in pH, or a reduction in SF concentration may be used, in accordance with the know-how acquired during silk ink development (Paragraph 6.1).
  • Vaccines Two distinct studies have been conducted, i) Stabilization of vaccine in SF solution - This is a fundamental study to investigate the SF chains-vaccine interaction in solution over a prolonged exposure time. The study is preparatory for device-oriented application. SF solution hybridized with increasing amount of reconstituted vaccine may be stored at 4°C, 25°C, and 37°C for 1, 3, and 7, 14 and 28 days.
  • the stabilization of the trivalent vaccine investigated may be accomplished as regulated by the World Health Organization (WHO): 1) the vaccine should retain at least 1,000 live virus particles in each human dose after incubation at 37°C for 7 days and 2) virus titer should not decrease by more than 1 log 10 during storage.
  • Viral infectivity assay may be used to evaluate vaccine stabilization, by employing RT-PCR, as recently published.
  • printed trivalent vaccine solutions with and without SF may be used as positive controls, ii) printed silk inks that stabilize vaccines and integrate the vaccine reconstitution within the printing process. This is a device-oriented study. As made SF-vaccine solutions with increasing concentrations of vaccine may be printed on different substrates ⁇ e.g.
  • Glucose oxidase a flavin adenine dinucleotide dependent enzyme (GOD-FAD) may be used to manufacture silk-based glucose sensors.
  • the enzyme shows high substrate specificity for ⁇ -d-glucose oxidation with molecular oxygen: ⁇ - d - glucose + GOD - FAD ⁇ GOD - FAD ⁇ H 2 + ⁇ — d - gluconolactone
  • GOD - FAD ⁇ H 2 ⁇ GOD - FAD + H 2 0 2 ⁇ -d-glucose is oxidized to ⁇ -gluconolactone with concomitant reduction of GOD-FAD.
  • the reduced form of GOD-FAD is regenerated to its oxidized form by molecular oxygen to produce hydrogen peroxide.
  • glucose oxidase derived from Aspergillus niger
  • SF has already shown to provide a structural and functional role in interfacing the biological milieu with electrodes and may also serve to immobilize the enzyme.
  • the electric signal generated from the reaction can be monitored by any suitable means.
  • SF-glucose oxidase ink may be co- printed with a silk ink hybridized with peroxidase and a chromogenic system (3,5-dichloro-2- hydroxybenzenesulfonic acid/4-aminoantipyrine).
  • a chromogenic system 3,5-dichloro-2- hydroxybenzenesulfonic acid/4-aminoantipyrine.
  • the stability of the proposed hybrid solutions may be evaluated as made and after storing them for 1, 3 and 7 days at 4°C and 22°C.
  • a commercial colorimetric glucose sensor may be used as control.
  • Antibiotics SF solution hybridized with increasing amount of antibiotics may be stored at 4°C, 25°C, 37°C and 45°C for 0, 1, 3, 7, 14 and 28 days (tetracyclines may be protected for the whole time from light exposure). Stabilization may be evaluated by printing a pattern with a gradient of antibiotics on tissue culture plastic (TCP) with previously cultured bacteria strains (e.g., E. Coli ATCC 25922 and S. Aureus ATCC 2593-cultured for 18-24 hours, to an optical density (OD600) between 0.8 and 1 or equivalent to 107-108 CFU/ml).
  • TCP tissue culture plastic
  • bacteria strains e.g., E. Coli ATCC 25922 and S. Aureus ATCC 2593-cultured for 18-24 hours, to an optical density (OD600) between 0.8 and 1 or equivalent to 107-108 CFU/ml.
  • Effectiveness in control of the topographical-selective destruction of bacterial culture may be evaluated by measuring zones of clearance, when compared with positive controls (inkjet-printed fresh antibiotic hybrid inks and antibiotic solutions (without SF) with known concentration of active therapeutic).
  • positive controls inkjet-printed fresh antibiotic hybrid inks and antibiotic solutions (without SF) with known concentration of active therapeutic.
  • SF solution hybridized with antibiotics may be printed with a controlled pattern and a biological gradient on gauzes, while bacteria strains may be cultured on a TCP as previously described.
  • the printed gauzes may be then applied to the bacterial cultures and the effectiveness of antibacterial activity may be evaluated by measuring the zones of clearance, when compared to a positive controls (antibiotic solution inkjet printed on gauzes).
  • GFs osteogenic and chondrogenic growth factors
  • ES-SF electrospun silk fibroin
  • h- MSCs response to GFs release may be evaluated at days 7, 14 and 21 with RT-PCR.
  • the total RNA may be extracted from h-MSC-seeded scaffolds with TRIzol®
  • RNA DNA
  • cDNA complementary DNA
  • Superscript Reverse Transcriptase II Invitrogen, Carlsbad, California
  • RNasin Promega
  • Quantitative RT-PCR may be performed with an ABI Prism 7900 HT 139 (Applied Biosystems). Each PCR reaction may contain 9 ⁇ of cDNA, 0.5 ⁇ 1 of both forward and reverse primers (10 ⁇ ), and 10 ⁇ of SYBR Green (Applied Biosystems).
  • the cycling conditions may be, for example: 50°C for 2 minutes, initial denaturation at 95°C for 10 minutes, and 45 cycles of 15 seconds at 95°C and 1 minute at 60°C.
  • Relative quantification of target gene expression may be achieved first normalizing to an endogenous reference gene (housekeeping gene GAPDH) to correct different amounts of input RNA, and then relating the expression of the target genes to a reference sample (h-MSCs extracted from relative control without GFs) using the -2AACt method.
  • h-MSC cultured with standard procedures on TCP may be used as control.
  • the substrate is a vital component of UP fibroin-based biomaterials.
  • the deposition of silk inks on the substrate may be affected by adsorption, which affects the structural, functional, mechanical and biological properties of the deposited proteins.
  • different choices of substrate may influence the properties of the biomaterials, bringing unique features to the end product.
  • silk-based UP substrates are currently under further investigation as silk-based UP substrates in our laboratory. Among these, are plain paper (used both as a 'standard' substrate and for colorimetric sensing applications), silk-microneedle sheets (for therapeutic and vaccine delivery), silk-based electrospun mats (used for tissue engineering and therapeutics applications), silicon wafers (for microelectronics and biological assays
  • the morphology of the ink-substrate interfaces for all the aforementioned substrates (diagnostics are available in-house) prepared in accordance with the present application can be evaluated using suitable techniques, such as through scanning electron microscopy (SEM), and atomic force microscopy (AFM).
  • SEM scanning electron microscopy
  • AFM atomic force microscopy
  • detachment force measurements at the silk ink/substrate interface for different crystallinity of SF-based inks may be investigated through AFM measurements, as previously reported. Characterization of the printed fibroin structure on different substrates may be studied with FTI and Raman spectroscopy for both neat SF and hybrid silk inks.
  • Example 2 Keratin Ink.
  • a keratin-based ink was prepared using wool as a starting material.
  • the following protocol was used.
  • the delipided wool fibers were then cut into short fibers, 3 mm long.
  • the solution was then filtered through a stainless steel sieve (#200) and dialyzed in dialysis cassettes (3,500 MW cut-off) against distilled water (8 liters) for 72 hours (changed every 6 hours).
  • the so obtained keratin solution was then centrifuged twice (5°C, 9000 rpm, 20 min per cycle).
  • the regenerated keratin solution was then concentrated to 7 wt% (70 mg/ml) through centrifugation in vacuum.
  • the so obtained regenerated ink was then used for ink jet printing as described before with silk fibroin.
  • the solution of keratin at 6 wt% has substantially the same rheological properties of the one of silk fibroin at the same concentration.
  • the MW of the so obtained keratin is around 40-60 kDa with a second band at 15-20 kDa.
  • Example 3 Demonstration and characterization of silk fibroin ink and its utility in inkiet printing.
  • Silk is generally considered as a protein polymer that are usually synthesized within specialized glands and then spun into fibers by some Lepidoptera larvae such as spiders, silkworms, mites and flies [1-3]. Silks generated by different species differ widely in composition, structure and their mechanical and chemical properties. In this work, efforts will be focused on the silk generated from the domesticated silkworm, i.e. Bombyx mori, partially due to the convenience to the silk source and the extensive experience and knowledge that the Department of Biomedical Engineering at Tufts University has gained in the past two decades.
  • each of the different silks has a different amino acid composition that further determines the mechanical properties for their specific functions and the forms of the end product such as reproduction as silk cocoons, silk webs, and etc. Even within the "same" type of larvae - for example Bombyx mori silkworms - the silkworms from different locations slightly differ. In this work, we mainly discuss the silk fibroin regenerated from the silk cocoons from Japan.
  • Silkworm silk fibers have been used in biomedical applications, particularly as sutures for wound ligation. However, some biological responses to the protein were found, which raised questions about the biocompatibility of the protein [6-8]. There have been some difficulties in identifying the exact source that causes the biological responses due to the lack of detailed characterization of the silk fibers prepared under different conditions.
  • the silk from Bombyx mori silkworms contains at least two main silk fibroin proteins (i.e. light and heavy chains with the molecular weight of ⁇ 25 and 325 kDa, respectively) that are encased in a coat of sericin.
  • a continuous silk thread (with a length over 1 kilometer) can be drawn from a single silk cocoon.
  • the fibroin is a huge molecule consisting of both amorphous region ( ⁇ l/3, commonly termed as Silk 1) and crystalline portion ( ⁇ 2/3, Silk II), as shown in Figure 1.1.
  • Silk I is a water-soluble structure while Silk II excludes waters and is therefore insoluble in water and some other mild acid and alkaline solutions [13].
  • Stfucnare silk II (cxystalBne structure) aoa-cr staiime stmemrs silk 111 (usst&hlc structure)
  • Figure 1.1 Structure of silk fibers [13].
  • the crystalline portion contains repetitive amino acids along its sequence (-Gly-Al- Gly-Ala-Gly-Ser-), resulting in an antiparallel beta sheet. And it is this beta sheet structure that leads to the extraordinary stability and mechanical properties of the fiber such as remarkable strength and toughness.
  • the toughness of silk fibers is found to be even greater than the best synthetic materials, including Kevlar [14]. And in terms of strength, silk is significantly superior to most of commonly used polymeric biodegradable biomaterials such as collagen. A comparison of the mechanical properties of silk and other biodegradable materials is shown in Figure 1.2.
  • FIG. 1.2 Mechanical properties of biodegradable materials [13].
  • Silk has been processed to a range of biomaterials such as films, gels, fibers and sponges.
  • the starting point of those silk-based materials is the regeneration (alternatively called extraction) of silk fibroin protein from silk fibers.
  • the regeneration of silk protein (for printable silk ink grade) from Bombyx mori silk fibers/cocoons is shown in Figure 1.3 and briefly described as followings
  • Figure 1.3 Schematic of the silk fibroin extraction procedure [15]. 1 Fill a 2 liter glass beaker filled with 2 liters of ultrapure water and heat until boiling;
  • LiBr lithium bromide
  • the entire extraction process takes about 4 days.
  • the resulted silk solution can be used for printing as it is or can be doped with appropriate dopants for specific applications.
  • the extracted silk fibroin can be further processed into different material formats for a range of potential applications, as shown in Figure 1.4 & 1.5.
  • Figure 1.4 Some of the popular material formats that can be processed from extracted silk fibroin [15].
  • Siik gels One important material option for silk-based biomaterials is the formation of hydrogels.
  • Silk hydrogels can be formed through vortexing (without needing to contact the solution with a probe), sonication (a simple method to produce silk gels), and the application of electrical current (the gelation process is reversible by reversing the polarity of the control voltage).
  • Silk films are of particular interest for bio- optics and bio-photonics applications due to their outstanding transparency and surface smoothness.
  • Silk films can be readily fabricated using both spin-coating process (for extremely thin films with the thickness ranging from a few nanometers to submicron; the thickness can be controlled by adjusting the concentration of the silk solution and spin-coating rate.) and soft-lithograph-like casting process (for films with the thickness of a few microns to hundreds of microns).Furthermore, pouring the silk fibroin solution on to a pre-patterned substrate can reproduce silk films that replicate the patterns on the substrate. fiks on
  • FIG. 1 Biomedical applications of various silk material formats [15].
  • Silk sponges Biomaterials play a key role in tissue engineering. Silk sponges (as a versatile 3D porous scaffolding material) allow cells seeded within or on the matrix and have the advantage of being able to degrade into biocompatible fragments afterwards. Silk fibroin offers versatility in terms of matrix design for a number of tissue engineering needs. Aqueous based porous silk sponges can be fabricated using variable size salt crystals as porogen and manipulating the concentration of silk solution and the salt size.
  • Silk fibers are of particular interest as biomaterials due to the increased surface area and rougher topography that facilitate cell attachment.
  • Silk fibers can be prepared by directly drawing the fibers from silk solution or by electrospinning.
  • Silk fibers can be produced in a wide range of diameters (ranging from a few nanometers to tens of microns).
  • inkjet printers Compared to laser printers (that use dry ink, also known as toner, static electricity and heat to print), inkjet printers use liquid inks and nozzles (usually multiple nozzles needed) to spray drops of ink directly onto the substrates.
  • a typical inkjet printer includes: a) print head - that contains a series of nozzles that are used to spray the ink drops; b) ink cartridge - that contains the ink; c) stepper motor - that moves the print head back and forth across the substrate.
  • inkjet printers use piezoelectric nozzle technique for precision printing, which use piezo crystals that vibrate when receive a tiny electric charge. When the crystal vibrates inward and out ward, it pulls and forces a tiny amount of ink and sprays it out of the nozzle.
  • inkjet printer from FUJIFILM, Dimatix Materials Printer DMP-2800, as shown in Figure 1.6. It uses piezoelectric inkjet technology and MEMS fabrication processes (for cartridges, nozzles and etc.).
  • Figure 1.7 The schematic of the key components of DMP 2800 inkjet printer [16]. As shown in Figure 1.7, the DMP-2800 series printer works with a maximum printable area of A4 size substrate (8x11 inch) with a disposable (but reusable with certain modifications/tweaks] piezo inkjet cartridge. The maximum height of printable substrate is up to 25 mm. It also has the ability to heat up the substrate up to 60 degree C. In addition, there is a fiducially camera available allowing real time watching the formation of the drop as it is ejected from the nozzle.
  • A4 size substrate 8x11 inch
  • the maximum height of printable substrate is up to 25 mm. It also has the ability to heat up the substrate up to 60 degree C.
  • there is a fiducially camera available allowing real time watching the formation of the drop as it is ejected from the nozzle.
  • the Dimatix Materials Desktop Printer DMP 2800 is a convenient laboratory tool that enables users (i.e. students, researchers and engineers) to evaluate the use of specific ink (i.e. silk fibroin solution in our case) for new and proof of principle technology development with extensive flexibilities to optimize process parameters for user oriented applications.
  • Paper i.e. polyimide
  • poyethylene PET
  • fabrics such as cotton, nylon, polyester
  • metals such as aluminum foil, copper foil, stainless steel foil and etc.
  • liquid crystal polymer palladium, and glass.
  • Conductive silvers conductive inorganics (non silver ink, such as ITO inks), conductive organics (such as OLED), single wall carbon nanotubes (SWCNTs), insulators, polyimides, photoresists, resins, and UV curable inks.
  • conductive inorganics non silver ink, such as ITO inks
  • conductive organics such as OLED
  • SWCNTs single wall carbon nanotubes
  • insulators polyimides
  • photoresists photoresists
  • resins and UV curable inks.
  • conductive inks For different types of conductive inks, they usually have a wide range of ink properties including viscosity, density, surface tension, and dispersion stability. Therefore, it is necessary to optimize the printer parameters such as the volume of the jetted ink, the gap distance between droplets, the printing frequency, temperatures of the jetted ink and the substrate, and the sintering/curing mechanism performed after printing.
  • printer parameters such as the volume of the jetted ink, the gap distance between droplets, the printing frequency, temperatures of the jetted ink and the substrate, and the sintering/curing mechanism performed after printing.
  • One of the most popular applications of using inkjet printer for conductive printing is rapid printing of RFID tags.
  • it is a rather challenging endeavor since precise control of the desired conductivity and pattern designs (on non-perfect substrates, for example, on non-glossy rough papers).
  • conductive inkjet printing for RF applications jets the single conductive ink droplet from the nozzle to pre-defined position (usually controlled by computer and a precise motor stepper) - therefore, no harsh chemicals as the etching waste created -resulting in an economical and ecological fabrication solution.
  • Silver nano-particle inks are and usually selected and commonly used for good metal conductivity.
  • a sintering process either by applying heat or UV exposure (to remove excess solvent and to remove material impurities) is usually needed, which also enhance the bond strength between the ink and the as-printed substrate. Note that an immediate sintering process is essential, because the silk ink begins to oxidize that would render the conductivit of efficiency of the metallic patterns.
  • Figure 1.8 SEM images of inkjet printed silver nanoparticle ink before and after sintering at 100 degree C for 15 minutes [17].
  • Figure 1.9 An example of inkjet printed RFID tag with a working frequency at 2GHz
  • Figure 1.10 SEM image showing human fibrosarcoma cells after inkjet printing [19].
  • DMP-2800 Inkjet printer from FUJIFILM Dimatix, Inc to directly print regenerated silk fibroin protein.
  • the DMP-2800 printer can create your own patterns and load BMP patterns over an area of about 200*300mm.
  • the printer allows the substrates up to 25mm thick with an adjustable Z height. It also includes 16 piezo-based jetting nozzles at 254 ⁇ spacing and a fillable cartridge. In this way, we invent a method to regenerate silk fibroin protein as the ink to match specific fluid requirement of this printer.
  • the printed silk protein is biocompatible and can be further functionalized by mixing the silk ink with appropriate dopants (including both organic and inorganic ones) for specific applications.
  • the DMP-2800 is a powerful laboratory tool which has capabilities to allow user to optimize process parameters, like nozzle voltage, substrate height, and wave form. Different from other commercial printer, DMP-2800 provides multi-layer printing and allows alignment process when using multiple cartridges and matching the origin point on the substrate. To brief introduce the operation of the printer, the process includes creating pattern, loading ink, setting printing permanents.
  • Pattern Editor allows you to modify pattern of drops for printing, so it is good for some fine and small scale patterns, for example, patterns from Figure 2.1. However, it takes a long time to create a complex structure pattern for printing. Patterns like Figure 2.2, you need transform to BMP file first, and then import them to DMP software.
  • Figure 2.2 Patterns for BMP pattern editor.
  • the ink which you fill into the cartridge need go through 0.22 ⁇ filter first, because the size of a nozzle is 26 ⁇ and the volume of a drop is lOpL. It means the nozzle is easy clogged by particle size larger than 0.22 ⁇ .
  • the system will automatic calculate the Cartridge Mounting Angle determined by drop spacing specified in the pattern.
  • Table 2.1 to compare the relation of saber angle, resolution, and drop spacing.
  • the system will move the cartridge to the right side of the platen, positioning the nozzles over the drop watcher camera system.
  • Another important parameter should be set up carefully is the cartridge print height according to the substrate thickness. If the substrate thickness is less than 0.5mm, the printable range is 210mm*315mm. If the substrate thickness is between 0.5mm to 25mm, the printable range is 210mm*260mm. And the repeatability distance is ⁇ 25 ⁇ .
  • the last step before printing is alignment process through Fiducial Camera from the tools menu on the DDM window. First, calibrate the position of a new cartridge or head angle by setting the Drop Offset automatic or manual from tools menu. Second, set the printing origin point and reference point for multiple layers printing. Table 2.1 Resolutions relationships
  • the main parameter includes nozzles voltage, nozzle temperature, meniscus set point, cleaning cycles, and waveform.
  • Figure 2.3 Cartridge setting screen- voltages setting.
  • Meniscus Vacuum is a negative pressure for keeping the meniscus at the edge of nozzle. Change the value of meniscus vacuum depends on the viscosity and surface tension of the ink. The typical meniscus vacuum value of water is 4 inches. If the meniscus vacuum number is not correct, it would affect the performance of ink with high frequency.
  • the printer has drop watch camera which allows you to real time monitor drop performance. In this way, the camera will help you to make sure the nozzles you choose performance uniform.
  • Figure 2.4 Cartridge Settings Cartridge Tab.
  • the cleaning cycle table lets you setting nozzles cleaning process before, during and after printing.
  • Setting cleaning cycle before printing gives a uniform start every running. Cleaning cycle is very import for some high viscosity, because setting cleaning cycle during printing prevents the ink from clogging.
  • Setting cleaning cycle after printing help you maintenance nozzles, as shown in Figure 2.5.
  • the DDM software has a standard 4 steps waveform which is good for normal ink (viscosity: 11-12 centipoises; surface tension: 28-32 dynes/cm).
  • the 4 steps include start, phase 1, phase 2, and phase 3.
  • the basic idea for those 4 steps is use a bias voltage to control piezo to suck a drop of ink and jet it with a controlled velocity. 2 ⁇ 1 Waviform Start
  • phase 1 set the voltage level to 0 and hold it for 3.584 5.
  • the voltage brings the piezo back to a neutral straight position with chamber at its maximum volume.
  • the fluid is filled into chamber. From the Figure 2.7, it shows meniscus at the nozzle edge.
  • the phase 2 is firing pulse, as shown in Figure 2.8.
  • the steepness of the slope provides the energy for initial ejection and it is followed by a hold period.
  • the voltage increases to 100% level and holds it for 3.712 3. A this point, the chamber starts to jet a drop of ink. According to the hold time and voltage volume, the velocity of a drop can be calculated.
  • the last phase of the waveform is return to standby, as shown in Figure 2.9.
  • the voltage level decreases to 70% and hold it for 3.392 ⁇ $ that is designed for prevent the printed head from sucking air back in.
  • the voltage level brings to 40% level and chamber back to the standby position.
  • solvent based ink usually contains some poisonous chemical material.
  • silk is processed in an all water-based, room temperature, neutral pH environment, is mechanically stable, edible, biocompatible, and implantable in the human body. Given the favorable material properties, the use of silk-based inks can be important for a variety of controlled chemical and biological material fabrication on the micro-and nano- scale.
  • a Water b sed Inks
  • the role of the humectants is to preserve the water content in ink, so that it does not clog and dry out print head nozzles. People usually use glycerol, ethylene glycol as the humectants in the water based ink.
  • Viscosity is a physical property that is often manipulated to make jet-able fluids. Viscosity is the reciprocal of fluidity and indicates resistance to flow. The flow speed decreases as viscosity increases. Temperature increases fluid flow in
  • displacement occurs.
  • low temperatures push fluids towards their ordered state, and as fluids become more ordered, they also increase in viscosity.
  • heat can be applied to decrease apparent viscosity (increase fluidity), and the DMP ink jet print head contains a heater thereby increasing the jettability window for viscous fluids.
  • the ideal viscosity for inkjet printer to print is 1 lcentpoises and the viscosity of water at room temperature is 1 centipoises.
  • Polyvinyl alcohol and glycerol add to water based ink as the viscosity to increase the viscosity. Viscosity adjuster keeps ink at proper thickness so that it can be jetted smoothly and stabile.
  • the role of the buffer is to maintain the PH level in the ink.
  • Degassing Additionally the fluid may need to be degassed to remove any dissolve gas which inhibits jetting. Typical degassing can be done with a vacuum (A negative pressure of 2 psi for 1-2 hours maybe sufficient or up to only 50mbar),
  • the parameter of viscosity and surface tension is a pair of combine parameter. Fluid with surface tension higher than 44 combines with viscosity lower than 10 also works for DMP 2800 printer by modifying the waveform.
  • Silk solution is that silk is easy getting ⁇ sheet when it is mixed with surfactant and viscosity adjuster. So, we just add surfactant, like Tween 20, to silk solution. To increase the viscosity, adjust the waveform to compensate the viscosity.
  • surfactant like Tween 20
  • the silk solution with surfactant (for example, Tween 20 from Sigma-Aldrich Co.) and water in a volume ratio of 17:2:1 (i.e. 1700 ⁇ iL of ⁇ 6.25% silk fibroin solution, 200 ⁇ , of Tween 20 and 100 ⁇ of water);
  • the ratio of the mixture is optimized for Tween 20 and other biological or chemical surfactant (for example, glycol, ether, and etc.) can be also used with modifications of the mixture ratio.
  • Surface treatment of the printing nozzle(s) can also improve the formation of silk ink drops.
  • the printable substrates using silk fibroin inks are limitless, simply depending on the available inkjet printers.
  • the printable substrates include, but not limited to, the followings:
  • the DMP-2800 printer uses the DMP-2800 printer to print some silk patterns, like dots, signal line, and 2D patterns, on both hydrophilic and hydrophobic substrates.
  • the resolution of printing affects by viscosity and surface tension of the silk ink. Also the resolution of pattern depends on roughness of substrate and nozzle size.
  • the DMP-2800 printer provides a lOpl size nozzle to make patterns, so one drop size is around 25 ⁇ and the width of a line is around 40um on the hydrophilic substrates.
  • a signal layer line will give the interface between dots, and a 2D pattern presents interface between lines.
  • the voltage is function of drop size and drop velocity. So voltage setting depend on height level what you want the nozzle above your substrate and the drop size your want to print. But voltage level below 15 V, the silk ink will not come out due to the surface tension of silk ink. High Voltage setting gives you more volume of the drop.
  • Figure 4.1 shows silk lines on silicon wafer under 15v, 20V and 25v voltage printing, and the width of silk lines are 65 ⁇ , ⁇ , ⁇ . Obviously, High voltage printing gives more width lines due to increasing the drop volume.
  • Figure 4.1 Silk Lines printed under different voltag: 1) 15v voltage, 65um; 2) 20v voltage, lOOum; 3) 25v voltage, llOum. .1,2 aveform
  • the surface tension of the ink is about 36 dynes/cm. So we use the waveform which is developed by the Dimatix Company.
  • spitting process After printing, spitting process provides protect nozzle from clogging. Spitting designed to ejecting some drops ink from the chamber. It lets the fresh silk drops reach to the meniscus to replace the old one.
  • Figure 4.2 Waveform for silk ink printing.
  • Figure 4.3 shows a silk line on the acrylic with 25v and one nozzle printing, and it gives 40 ⁇ width silk line.
  • Figure 4.4 is silk line with 240 widths still under 25v printing. However, the width of the line become much more width than Figure 4.3, because it printing by 7 nozzles.
  • Figure 4.5 is the drops from lOpL nozzles, and the voltage value set 23V, jetting frequency is 5 KHz.
  • FIG. 4.5 Silk drops. ,2 V rious silk atterns mlng directly mkjet rir ⁇ ng technique
  • Figure 4.6 and Figure 4.7 show silk dots printed on silicon wafer and aciylic, respectively.
  • the voltage value is 15v and jetting frequency is 1 KHz.
  • the size of dots is 40 ⁇ on silicon wafer and 30 ⁇ on acrylic.
  • FIG. 4.6 Silk dots (40 ⁇ ) on silicon wafer.
  • Figure 4.7 Silk dots (30 ⁇ ) on silicon acrylic.
  • Figure 4.8 shows silk lines which are printed with one nozzle and 15v on the silicon wafer.
  • figure 4.9 shows the SEM picture of those one layer printing.
  • One layer printing is clear without any interface between drops. Comparing one layer printing with three layers printing, one layer patterns are more uniform and the edge of line is cleaner.
  • a rough edge shows on three layers printing (Figure 4.10), because the upper layer fluid causes capillary instability when the upper layers silk are printed. From the Figure 4.11, it indicates the first line is width than other 4 line, because the alignment of first line is not as good as other 4 lines.
  • Figure 4.12 shows serious capillary instability in a twenty layers pattern, so multiply layer printing is just suitable for low resolution patterns.
  • Figure 4.8 One layer silk pattern on silicon wafer.
  • Figure 4.9 SEM photo of one layer lines.
  • Figure 4.10 Three layers silk pattern on silicon wafer.
  • Figure 4.12 Twenty layers silk patterns on silicon wafer.
  • the method for printing multiple layers lines and cross lines is different.
  • the substrate is fixed during printing and the direction of printing among multiply layers lines is some.
  • the substrate is routed by 90 degree C after first layer printing, and then do the second layer printing. So the direction of the two layers is different.
  • the Figure 4.13 - 4.15 indicates capillary instability between two layers, and the edge of pattern shows a clean gradual capillary instability process.
  • Figure 4.15 SEM photo of cross silk line pattern (capillary instability).
  • One layer square pattern shows interface between lines. From Figure 4.16, there is less than 1 ⁇ width overlap between two lines. After applying laser point to the pattern, a diffraction grating patterns show on the wall due to the ⁇ ⁇ overlap, as shown in Figure 4.17. However, the overlap part of the pattern is disappeared after printing second layer pattern. So, the multiple layers give a smooth finish pattern ( Figure 4.18 and 4.19).
  • Figure 4.16 One layer 2D patterns.
  • Silk film is easily dissolved in the water. However it will not dissolve after alcohol annealing due to the formation of ⁇ sheet.
  • Figure 4.20 a) Silk Pattern before annealing; b) Silk Pattern after annealing. 43 Thickness of S k pattern
  • Silk provides a biologically favorable environment allowing them to entrain various biological and chemical dopants and maintain their functionality. Mixing Different chemical solution with silk solution gives different viscosity and surface tension which are affect thickness of pattern. Obviously, the number of printing layer is another important element affects the thickness of pattern. Preparing three kinds of silk solution include food color silk, high refractive index silk and pure silk, and then print them with some number nozzles.
  • Figure 4.21 - 4.23 shows the thickness of patterns are increased by the number printing layer. The thinnest pattern is less than lOOnm created by one layer food color silk pattern. According to Figure 4.24 the thickest pattern is pure silk pattern due to highest percentage silk in the solution.
  • Figure 4.21 Printing layers vs. thickness of food color silk patterns.
  • Figure 4.23 Printing layers vs. thickness of silk patterns.
  • Figure 4.24 Comparison of printing layers vs. thickness of different silk inks.
  • the printable substrates for silk ink include paper, glass, silicon, metals, cloth textiles and plastics. Those substrates can be divided two groups which are hydrophobic substrate and hydrophihc substrate. The drop size on hydrophobic substrate is sight smaller due to high surface energy.
  • the width of silk lines from Figure 4.8 is similar with the silk lines from Figure 4.25. However, the two patterns are supplied by different voltage. Silk patterns on silicon have slight large voltage value.
  • Figure 4.25 One layer silk patterns on acrylic. 5 Directly printing of functional silk devices using doped silk solution as the Ink
  • Silk fibroin has proved to be an effective material and matrix that can maintain the functionalities of dopants. Therefore, choosing the appropriate dopants (including both physical dopants - e.g. metallic nanoparticles, laser dyes, quantum dots and etc. - and biochemical dopants, e.g. cells, enzymes, bacterium and etc.) and mixing them into silk fibroin solution as the ink is a promising way to directly printing of functional devices using Dimatix DMP 2800 printer. In the following section, a series of functional silk devices (with different dopants) will be described as the proof of principle demonstrations.
  • dopants including both physical dopants - e.g. metallic nanoparticles, laser dyes, quantum dots and etc.
  • biochemical dopants e.g. cells, enzymes, bacterium and etc.
  • silk provides a biologically favorable environment allowing them to entrain various biological and chemical dopants and maintain their functionality.
  • Proteins and enzymes haven been previously doped into various silk material formats, especially silk films.
  • gold nanoparticles doped silk films that resonantly absorb incident light and convert it to heat, which can be potentially used as a biocompatible thermal therapy for in vivo medical applications such as tumor and bacterial killing.
  • the preparation of gold nanoparticle silk ink consist of the production of the print grade silk fibroin solution and synthesis of gold nanoparticles, followed by a simple mixing of the two solution with a certain ratio that is determined by applications. Briefly, pre-cut Bombyx mori cocoon pieces are boiled in a 0.02 M Na2C0 3 solution for 2 hours to remove sericin and boiled silk fibers are dried overnight and then are siddolved in a 9.3 M LiBr at 60 degree C for 4 hours. The lithium bromide salt is then removed from the silk solution through a water-based dialysis process.
  • the gold nanoparticle solution is prepared by adding 20 mL 1% a ⁇ HsC)?
  • Table 5.1 gives the main parameters for printing and the printing result is showed in Figure 5.2.
  • the printed Au-NPs doped silk device showed enhanced plasmatic absorption of green light (figure 5.3), resulting in a temperature increase of ⁇ 15 degree s with an irradiance of ⁇ 0.25 W/cm 2 .
  • the heating effects could be further improved and optimized by adjusting the Au-NPs concentration and layers of the printed structures, which could be potentially used for light-mediated patterned heating treatments.
  • Figure 5.2 Gold nanoparticles doped silk dots patterns printed on paper.
  • Figure 5.3 IR view of gold nanoparticles doped silk dots patterns exposed to green light radiation.
  • ELISA immuosorbent assay test
  • ELISA is a widely used test to identify certain substance using antibodies and the colorimetric change as the sensing/diagnostic mechanism.
  • the enzymes used in ELISA tests need to be stored at low temperature for maintaining the bioactivities. It has been proved that silk can help to maintain the functionalities of the doped enzyme at room temperatures without fridge-storage. Therefore, directly printing of enzyme doped silk patterns (in a precise way) holds great opportunities in such as rapid and low volume screening test, food allergens, and toxicology applications, as shown in Figure 5.4.
  • Figure 5.4 Printed HRP doped silk changes its color (to blue) when sprayed TMB solution.
  • the pattern is printed after bacterial overnight growth (Method two). There is an arrow in the in the Petri dish after 9 hours incubate ( Figure 5.6).
  • Figure 5.5 Two clean bacterial inhibition zones in bacterial growth petri dish.
  • Figure 5.6 Bacterial growth inhibition zone (in the shape of an arrow).
  • Food coloring alternatively called color additive, imparts color when added to food or drink, and is used widely both in commercial food production and in domestic cooking.
  • the color silk patterns remain its original pattern after 2 hours vacuum annealing. Also it is survival after dry cleaning process, as shown in Figure 5.8.

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Abstract

La présente invention concerne des formulations d'encre à base de biopolymères qui sont utiles pour l'impression par jet d'encre et d'autres applications. L'invention concerne également des procédés associés.
PCT/US2013/072435 2012-11-27 2013-11-27 Encres à base de biopolymères et leur utilisation WO2014085725A1 (fr)

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US16/029,316 US10731046B2 (en) 2012-11-27 2018-07-06 Biopolymer-based inks and use thereof

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US10731046B2 (en) 2020-08-04
EP2925822A4 (fr) 2016-10-12
US20190177560A1 (en) 2019-06-13
US10035920B2 (en) 2018-07-31
EP2925822A1 (fr) 2015-10-07
US20150307728A1 (en) 2015-10-29

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